How to Obtain a Sustainably Preferential Supplier Resource Allocation? A Model Based on the S-O-R Framework from a Supplier’s Perspective

Abstract

As pivotal members of upstream channels, suppliers wield significant influence on supply chains’ competitive advantage through their abundant resources. Buyers often engage in supplier development to access scarce resources, yet the motivations guiding suppliers’ responses remain unclear. This study elucidates suppliers’ cognitive processes and the factors influencing their decisions to allocate resources. Utilizing the S-O-R framework, we construct a moderated mediation model to verify motivational drivers and explore interactions among mediators. A survey involving 246 Chinese manufacturing suppliers was conducted, employing path analysis with bootstrap validation. It aimed to confirm how supplier-perceived relationship value, trust, and switching costs mediate between supplier development and resource allocation decisions. Our study delves into how supplier development impacts resource allocation, emphasizing psychological motivation within the S-O-R framework. We analyze three dimensions of supplier value perception: relationship value, trust, and switching costs. These factors influence physical and innovation resource allocation differently. While all prompt the prioritization of physical resources, only relationship value encourages innovative resource sharing, with switching costs hindering this. Supplier-perceived trust acts as both a mediator and moderator, enhancing positive effects on physical allocation and mitigating negative impacts on innovation resource sharing. This study advances the S-O-R framework’s applicability, providing novel insights into supplier resource allocation.

1. Introduction

The competitiveness of a supply chain mirrors the bucket effects theory, where the weakest link sets the upper limit of the overall advantage. If a buyer fails to attract key upstream resources, the upstream supplier becomes a bottleneck, hindering the buyer’s competitive edge. Leading suppliers offer critical support such as innovative ideas, technical assistance, and market insights to buyers, which are often shared among competitors [1,2]. For example, Weichai Power, China’s largest parts supplier, serves strategic customers like Shaanxi Heavy Duty Special Truck, FAW Jiefang Group, and Sino-Trunk (https://www.weichai.com/ (accessed on 1 June 2024). This situation compels buyers to engage in “reverse marketing” efforts to secure priority access to resources [2,3,4]. However, resources are finite, leading to selective allocation by suppliers and unequal distribution among customers [2]. For example, Weichai Power allocates a higher proportion of resources to FAW Jiefang Group over Sino-Trunk (https://www.weichai.com/). Therefore, the question arises: what motivates suppliers to prioritize specific buyers in the allocation of valuable resources?

Research indicates that supplier development is a common strategy employed by buyers to optimize supplier resources [5]. Supplier development entails long-term collaborative efforts between buyers and suppliers aimed at enhancing the supplier’s product technology, quality, delivery, and cost capabilities [6], fostering mutual growth and a win–win philosophy. Supplier development, initiated by the buyer, is a means by which to enhance buyers’ purchasing, innovation, and other performance [7,8,9]. Subsequent research has found that these activities achieve improvements in buyer performance by enhancing supplier performance [10,11]. Therefore, buyers achieve high levels of performance by leveraging the limited resources provided by suppliers. Effectively prioritizing access to sufficient quantities of high-quality resources is crucial when implementing supplier development activities within a shared supply base. Existing research predominantly employs social exchange theory and the resource-based view to explore concepts such as supplier resource allocation and preferred customer status, yet it overlooks the crucial role of suppliers’ intrinsic value perceptions in resource allocation [4,12,13,14,15]. However, a supplier’s internal value judgment determines the direction of resources; therefore, it is necessary to explore from a psychological perspective how buyer-initiated supplier development activities influence supplier resource allocation. Only recently has the critical role of the psychological dimension in responding to supplier development programs been explicitly acknowledged [16].

The S-O-R (stimulus–organism–response) framework delves into how external stimuli prompt internal psychological assessments that drive specific behaviors [17]. This framework elucidates the internal factors influencing individual responses to external stimuli, encompassing cognitive processes, emotions, attitudes, and other personal factors. In the context of supplier development, which serves as an external stimulus, buyers aim to enhance supplier capabilities through training and technical support, expecting suppliers to prioritize them in resource allocation (response). Utilizing the S-O-R framework enables us to probe into the internal motivations (organism) guiding why suppliers prioritize certain buyers for scarce resources. Thus, a mediation analysis-based research strategy is warranted to elucidate why and how suppliers prioritize resource allocation in response to buyer-led development efforts.

2. Literature Review

2.1. Supplier Value Perception

Previous studies have proposed concepts akin to supplier value perception. For instance, Qiao et al. (2022) utilized “supplier-perceived relationship attractiveness” as a moderator to explore the influence of environmental assessment and collaboration on environmental commitments, encompassing economic and status expectations within relationships [16]. Similarly, existing scholars introduced “relationship benefits perceived by suppliers”, investigating how black-box supplier involvement in buyer-led innovation hinges on perceived relationship benefits [18]. Furthermore, other scholars examined supplier-perceived value in the B-to-B context, comprising financial, strategic, and co-creation value [19]. However, in our study, we delineate a clear research phenomenon, employing keywords such as “preferred customer status”, “supplier resource allocation”, “supplier preferential treatment”, “supplier satisfaction” and “customer attractiveness” to uncover insights into suppliers’ internal value judgments (see

Table 1. Antecedents of supplier resource allocation.

Drivers of Supplier Resource Allocation	Reference
Relationship value
High purchase volumes	Brokaw and Davisson (1978) [20], Williamson (1991) [21], Bew (2007) [22], Steinle and Schiele (2008) [23]
Profitability	Moody (1992) [24], Bew (2007) [22], Praxmarer-Carus et al. (2013) [25], Schiele (2020) [26]
Business opportunities	Brokaw and Davisson (1978) [20]
Cost reduction	Moody (1992) [24], Bew (2007) [22]
Technical competence	Essig and Amann (2009) [27]
Response to supplier requests and suggestions for improvement	Johnson and Fearon (2006) [28] Essig and Amann (2009) [27]
Adherence to agreements	Maunu (2003) [29], Essig and Amann (2009) [27]
Dedicated investments	Nyaga et al. (2010) [30], Pulles et al. (2022) [2]
Access to new customers/markets	Christiansen and Maltz (2002) [31], Ellegaard and Ritter (2007) [32], Hald et al. (2009) [33]
Customer’s ability to cope with changes	Fiocca (1982) [34], Ramsay and Wagner (2009) [35]
Knowledge transfer	Christiansen and Maltz (2002) [31], Hald et al. (2009) [33], Harris et al. (2003) [36]
Growth opportunity	Vos et al. (2016) [37], Hüttinger et al. (2014) [38], Schiele (2020) [26]
Innovation potential	Vos et al. (2016) [37], Hüttinger et al. (2014) [38]
Customer financial attractiveness	Baxter (2012) [39]
Relationship trust
Loyalty	Brokaw and Davisson (1978) [20], Williamson (1991) [21]
Trust	Blonska (2010) [40], Benton, Maloni (2005) [41], Nyaga et al. (2010) [30], Rindell et al. (2014) [42], Mungra, Yadav (2019) [43]
Commitment	Blonska (2010) [40], Benton, Maloni (2005) [41], Paul et al. (2010) [44], Nyaga et al. (2010) [30], Eckerd, Hill (2012) [45]
Satisfaction	Brokaw and Davisson (1978) [20]
Customer attentiveness	Moody (1992) [24]
Respect	Moody (1992) [24]
Fairness	Moody (1992) [24]
Strong bonds	Blonska (2010) [40]
Early supplier involvement	Moody (1992) [24]
Schedule sharing	Moody (1992) [24]
Communication and feedback	Moody(1992) [24], Maunu(2003) [29], Johnson and Fearon (2006) [28], Essig and Amann (2009) [27], Ahmed et al. (2020) [46]
Joint relationship effort	Nyaga et al. (2010) [30]
Cooperative relationships	Wong (2000) [47]; Forker and Stannack (2000) [48], Benton and Maloni (2005) [41], Leenders et al. (2006) [28], Essig and Amann (2009) [27]
Length of relationship	Ellis et al. (2012) [49]
Switching cost
Action-oriented crisis management	Moody (1992) [24]
Risk sharing	Christiansen and Maltz (2002) [31], Ramsay and Wagner (2009) [35]
Standardization of product	Christiansen and Maltz (2002) [31]
Level of transaction-specific assets	Hald et al. (2009) [33]
Demand stability	Ramsay and Wagner (2009) [35], Jenkins, Holcomb (2021) [50]
Patent protection	Fiocca (1982) [34]
Market stability	Fiocca (1982) [34]
Perceived share of cost	Praxmarer-Carus et al. (2013) [25]
Conflict in the relationship	Vos et al. (2021) [15]

).

Through an extensive literature review, the prioritization of supplier resources is primarily driven by the evaluation of the value a particular buyer can offer both presently and in the foreseeable future [4,25,26,37,38,49,51]. This value assessment encompasses various factors such as purchase volume, technology patents, capital infusion, innovation support, and process enhancement, alongside a buyer’s market influence leading to potential reputation enhancement and market expansion opportunities for suppliers [12,52]. Suppliers tend to prioritize buyers who demonstrate competency in meeting their needs, aligning with expectancy theory in psychology, wherein suppliers anticipate collaboration opportunities or increased profits from a buyer’s developmental actions and evaluate the nexus between their expectations and realized rewards to make resource allocation decisions. We categorize the anticipated benefits or rewards that suppliers expect to derive from specific buyer relationships as supplier-perceived relationship value. Moreover, apart from the tangible value inputs, supplier resource allocation behavior toward specific buyers is influenced by the relational dimension [1,2,3,14,38,41,43,53,54]. Extensive communication, frequent business transactions, and resource sharing foster a deep understanding of a buyer’s business and reputation, thereby engendering trust in reliable buyers and encouraging suppliers to commit resources. These aspects align with existing studies suggesting that supplier-perceived gains stem from both economic and socioemotional factors [51]. Simultaneously, relational theory in psychology underscores the impact of individual interactions on emotions, cognition, and behavior [55]. We categorize these factors that benefit from a dyadic relationship as supplier-perceived relationship trust; however, notably absent in the current literature is the consideration of supplier crisis awareness. In situations where a buyer engages with multiple suppliers for development initiatives simultaneously, suppliers may face pressure to reduce procurement volumes or terminate partnerships if others outperform them. This results in sunk relationship costs and prompts suppliers to seek new buyers while investing additional resources, leading to psychological sunk costs. To safeguard these investments, suppliers may prefer to continue collaborating with a specific buyer, which is consistent with behavioral investment theory. Furthermore, peer pressure may drive suppliers to secure contracts with buyers early in the development stage to ensure future business volume, thus giving rise to switching costs. Additionally, suppliers may actively seek partners to diversify and strengthen their customer base, further contributing to switching costs. We classify these elements as supplier-perceived switching costs, aligning with established concepts of dyadic relationship switching costs and dependency costs in extant literature [56,57]. In conclusion, supplier resource allocation for development activities is guided by three main factors: (1) the perceived value input from the buyer, encompassing both direct and indirect contributions; (2) the perceived quality of the buyer–supplier relationship, particularly trust; and (3) the perceived pressure of switching customers, including both tangible and psychological costs.

2.2. Supplier Resource Allocation

Suppliers possess a multitude of resources, as delineated into two primary categories in prior research: physical resources and innovation resources [2]. Physical resources, characterized by their tangible attributes, are relatively straightforward to safeguard due to their “seeing” and “touching” characteristics. Conversely, innovation resources predominantly consist of intangible assets such as patents, technologies, and emerging ideas still in the nascent stages of development projects, rendering them challenging to protect with conventional measures. Considering the distinctive attributes of these resources, it becomes imperative to investigate potential disparities in the underlying foundations of suppliers’ allocation decisions.

The strategic allocation of limited resources by suppliers is a cornerstone in shaping the competitive advantage of buyers and influencing the overall attractiveness of the supply chain. This allocation mirrors the concept of granting “preferred customer status” or offering preferential treatment, where suppliers prioritize specific buyers over competitors, thereby enhancing a buyer’s competitive position within the marketplace [1,13]. Physical resources and innovation resources collectively determine the comparative advantage of downstream customers. Regarding physical resources, decision-making processes involve the strategic allocation and prioritization of limited resources among various buyers, considering inherent capacity constraints. This intricate process includes the judicious distribution of scarce raw materials, the efficient utilization of equipment, and the strategic scheduling of deliveries. Conversely, in addressing innovation resources, the focus shifts to the critical role of knowledge exchange in fostering emergent business opportunities, product developments, or breakthroughs in process innovation [2]. This involves the dissemination of key technical insights and the cultivation of innovative methodologies. Based on the different characteristics of resources, suppliers have different tendencies in value judgment.

2.3. The S-O-R Framework

The S-O-R framework posits that environmental cues (stimulus) can evoke an individual’s internal assessment state (organism), influencing subsequent positive or negative actions (response) [17]. Prior investigations have examined the impact of external stimuli on subsequent behaviors by considering internal cognitive and psychological states, such as perceived value, benefits, and risks [18,58], underscoring the pivotal mediating role of an organism’s perception (organism) in bridging stimulus and response. This framework elucidates the internal factors influencing individual responses to external stimuli, encompassing cognitive processes, emotions, attitudes, and other personal factors.

Existing research has largely utilized the S-O-R framework to investigate online purchasing behavior and intentions [59,60,61]. However, its application in buyer–supplier relationship management remains limited. For instance, studies have explored the motivations of opaque suppliers in contributing to buyer innovation [18] and the mechanisms through which environmental assessment and collaboration influence supplier environmental commitments. In light of our research question, we consider supplier development as initiated by a buyer, thus representing an external driver for suppliers (stimulus). Whether suppliers are willing to prioritize resource allocation after accepting these development activities depends on their internal value assessment (response). Drawing from the S-O-R framework, we identify an organism’s internal state as a crucial mediator—a dynamic and intricate psychological process representing a supplier’s perception and interpretation of external stimuli. This internal state significantly influences a supplier’s attitude, decision making, and behavior in response to the buyer’s development activities; therefore, leveraging psychological theories elucidating individual behavior in interpersonal relationships, we introduce the concept of supplier value perception (organism) to explicate suppliers’ internal motivations. A buyer’s developmental initiatives activate a supplier’s perceptual system, evoking positive or negative emotions and cognitions, subsequently shaping the supplier’s resource allocation decisions. This framework sheds light on why some suppliers respond positively to supplier development actions while others are less enthusiastic.

3. Research Framework and Hypotheses Development

3.1. Research Framework

In the context of supplier development, which serves as an external stimulus, buyers aim to enhance supplier capabilities through training and technical support, expecting suppliers to prioritize them in resource allocation (response). When suppliers partake in supplier development initiatives initiated by buyers, they perceive signals indicating areas for improvement and buyers’ commitment to long-term cooperation. Throughout this collaboration, suppliers not only benefit from cost savings and capacity improvements but also foster deeper relationships with specific buyers. If buyers’ development activities are perceived as reasonable and beneficial, suppliers are inclined to allocate resources accordingly. Drawing from expectancy theory in psychology [62,63], suppliers evaluate the relationship between their investments and expected returns before making resource allocation decisions. Anticipated values include opportunities for corporate enhancement, innovation, and operational improvements [26]. Additionally, relational theory in psychology explains the impact of individual interactions on emotions, cognition, and behavior [55]. In supply chain management, this theory elucidates cooperative behaviors between suppliers and buyers, emphasizing trust, cooperation, and mutual benefit fostered through development activities. Suppliers are more inclined to support buyers through resource allocation if such a relationship is cultivated [8,18,48]. Moreover, the behavioral investment theory elucidates individual behavior in interpersonal relationships, focusing on the impact of investment on relationship maintenance [64,65]. The theory posits that individuals exhibit a greater inclination to persist in relationships commensurate with their investment, be it emotional, temporal, financial, or effort-based, even amidst challenges or adverse circumstances. Suppliers, similarly, invest in response to buyer-initiated development activities, encompassing endeavors such as acquiring new technologies, refining production processes, and elevating product quality. These investments, juxtaposed against the benefits accrued from meeting buyer demands, contribute to a supplier’s return on investment, thereby reinforcing their motivation to maintain the relationship. As suppliers navigate the fulfillment of buyer demands, the amalgamation of costs and benefits yields an investment return ratio, serving as a catalyst for their commitment to nurturing and sustaining the relationship. Nevertheless, certain assets allocated by suppliers present challenges in the seamless transfer to alternative buyers, thus influencing their strategic resource allocation. Incorporating the S-O-R framework, we integrate three psychological motivations for suppliers, which are informed by theories elucidating individual behaviors in interpersonal relationships. These include a supplier’s perceived value of the relationship, trust, and switching costs. Accordingly, we construct a conceptual model, as shown in Figure 1.

3.2. Supplier Development and Value Perceived by the Supplier

3.2.1. Supplier Development and Supplier-Perceived Relationship Value

In the complex context of supplier development, the substantial investments made by buyers in infrastructure and human capital firstly enable a supplier to have a deeper understanding of the value inherent in the buyer–supplier relationship, thus triggering the supplier to form positive expectations for cooperation. These investments by a buyer include investments in tangible assets and intangible technologies, such as advanced equipment, patents, copyrights, and organizational capabilities like communication, coordination, problem solving, and employee training [66,67]. Secondly, buyers’ investments in market influence, encompassing competitive positioning and industry reputation [38], may also affect the anticipated value of suppliers. Resolute and dependable buyers offer the assurance of forthcoming collaborative advantages. Through supplier development initiatives, suppliers gain insight into buyers’ procurement arrangements, empowering them to forecast allocated volumes, thereby amplifying their perceived value through scale effects and profitability. Finally, a buyer’s enhancements in operational processes, capabilities, and performance, coupled with investments in future growth prospects and innovation potential [68,69], confer upon suppliers enduring strategic advantages, shaping their expectations of lasting benefits from collaborative endeavors [25]. In summary, investments made during supplier development not only cater to current requirements but also psychologically elevate suppliers’ expectations of the buyer relationship, augmenting the perceived value of the partnership. This resonates with the core premise of expectancy theory, wherein expectations directly influence individual motivation and perceived value. Therefore, we propose the following hypothesis:

H1a: 

Supplier development has a positive impact on supplier-perceived relationship value.

3.2.2. Supplier Development and Supplier-Perceived Relationship Trust

Supplier development initiatives not only facilitate an in-depth understanding of buyers’ economic assets and operational capabilities among suppliers but also cultivate emotional reliance. Firstly, these initiatives typically span a prolonged duration and evolve through continuous engagement, which is exemplified by initiatives such as John Deere’s patient assistance to suppliers in identifying competitive gaps (https://www.weichai.com/ (accessed on 1 June 2024)). Such endeavors serve to establish an enduring and stable interactive relationship, wherein suppliers perceive a buyer’s commitment to their long-term improvement, fostering an emotional connection with a buyer [54]. Secondly, a buyer’s persistent support, unwavering commitment, and collaborative problem-solving pattern contribute to establishing a foundation of trust. This trust is built not only on a buyer’s capabilities but also on their integrity and sense of responsibility. Furthermore, suppliers witness a buyer’s continuous efforts and optimizations in production, distribution, and service through their participation in the development project [70], which enhances their positive perception of the buyer. This constructive and collaborative attitude is considered essential in cultivating emotional connections and trust within the framework of relationship psychology. Through frequent and meaningful interactions, a buyer not only provides economic support but also fosters reliability and trustworthiness on an emotional level [51]. This psychological support and cooperation are viewed as pivotal drivers in relationship psychology, motivating both parties to establish profound and resilient connections [71]. In summary, relationship theory underscores the critical roles of emotional dependence, ongoing collaboration, and a positive attitude in relationship building, ultimately nurturing a deeper level of trust between both parties. We put forward the following hypothesis:

H1b: 

Supplier development has a positive impact on supplier-perceived relationship trust.

3.2.3. Supplier Development and Supplier-Perceived Switching Cost

Suppliers engaged in supplier development projects not only perceive value enhancement and relationship trust but also demonstrate acute awareness of potential crises. Firstly, while buyer-initiated projects are frequently customized to align with their products, operational procedures, and organizational aims, the specialized characteristics of the resulting components and technologies pose obstacles for suppliers in their applicability to alternative buyers [2]. Thus, suppliers show heightened sensitivity toward switching costs, acknowledging the potential for irreplaceable losses due to the uniqueness of these specialized assets. Secondly, suppliers endeavoring to expand their clientele must diligently gather information from diverse markets and expend substantial time as well as resources in the identification of suitable potential buyers. Additionally, they are compelled to reallocate resources to conform with the distinct business requisites of these new ventures and innovate novel product solutions accordingly. Lastly, in scenarios where buyers engage multiple suppliers simultaneously in the same development project, certain suppliers may outperform others, resulting in the allocation of a greater share of the procurement volume to them. Consequently, the affected supplier may be compelled to actively seek new customers for their surplus production, further exacerbating the perceived switching costs [57]. In conclusion, the behavioral investment theory underscores the significance of perceived sunk costs and avoidable losses encountered by suppliers in supplier development projects. This perspective elucidates why suppliers sensitive to such dynamics tend to exhibit an elevated awareness of potential pitfalls, resulting in heightened sensitivity to switching costs. We propose the following hypothesis:

H1c: 

Supplier development has a positive impact on supplier-perceived switching cost.

3.3. Value Perceived by the Supplier and Supplier Resource Allocation

3.3.1. Supplier-Perceived Relationship Value and Supplier Resource Allocation

Suppliers who highly value their relationships anticipate substantial material benefits, such as increased orders, favorable pricing, and stable transaction terms in their collaborations. They gauge these expectations against actual outcomes, and when met or exceeded, their satisfaction and commitment to the relationship is enhanced. Drawing from expectancy theory [62], the fulfillment of expectations fosters active engagement and ongoing cooperation. Consequently, suppliers perceiving high relationship value are more inclined to proactively allocate resources to nurture and reinforce the relationship; however, the allocation of innovation resources is fraught with greater uncertainty, prompting suppliers to exercise caution. Throughout the new product development process, suppliers face the risks of contract termination and the potential appropriation of innovative outcomes [71,72]. Therefore, we anticipate that supplier-perceived relationship value will exert a stronger impact on physical resources than innovation resources. Accordingly, we predict the following:

H2a: 

The higher the supplier-perceived relationship value, the stronger the willingness of supplier physical resource allocation.

H2b: 

The higher the supplier-perceived relationship value, the stronger the willingness of supplier innovation resource allocation.

H2c: 

The effect of supplier-perceived relationship value on physical resources is stronger than on innovation resources.

3.3.2. Supplier-Perceived Relationship Trust and Supplier Resource Allocation

Suppliers often grant preferred customer status to buyers they profoundly trust, which is a distinction particularly evident when contrasting innovation and physical resources. The latter demands less intensive interaction compared to the former. As interaction frequency escalates, the richness and depth of exchanged information between suppliers and buyers notably increase. This enhanced communication is instrumental in fostering innovative ideas and tackling complex challenges. Importantly, these transactions transcend mere economic benefits, embodying a strong orientation toward relationship building [51]. Support and recognition significantly bolster suppliers’ confidence, empowering them to fully leverage their strengths in collaborative innovation projects. Consequently, it is hypothesized that the perception of relationship trust by suppliers exerts a more substantial influence on the allocation of innovation resources compared to physical resources. This heightened impact underscores the critical role of trust in facilitating open, creative engagements essential for innovation. We assume the following:

H3a: 

The higher the supplier-perceived relationship trust, the stronger the willingness of supplier physical resource allocation.

H3b: 

The higher the supplier-perceived relationship trust, the stronger the willingness of supplier innovation resource allocation.

H3c: 

The effect of supplier-perceived relationship trust on innovation resources is stronger than that on physical resources.

3.3.3. Supplier-Perceived Switching Cost and Supplier Resource Allocation

Suppliers have invested significantly in nurturing relationships with their existing customers, encompassing trust building, understanding customer needs, and adapting to evolving requirements, while also developing specialized expertise. Should a supplier contemplate substituting an existing buyer, they would face substantial additional costs, which are not limited to, but include, the following: (1) the outlay associated with gathering information on potential clients and forging connections with new, prospective parties; (2) the costs linked to adapting investments to suit the needs of new customers, particularly due to the specificity of existing assets; and (3) the forfeiture of relationship-specific assets previously allocated to incumbent clients, including deliberate investments in specialized entities or locations, as well as the subtler aspect of shared work skills and knowledge [45]. Despite discontinuing a relationship potentially appearing as a rational choice, it is often viewed as wasteful of prior investments. Considering the investment costs inherent in these established relationships and the additional costs required for establishing new connections, suppliers are inclined to maintain cooperative relationships, even if it necessitates compromises in resource allocation. The uncertainty and risks associated with innovation further accentuate the impact of high switching costs. Suppliers may exhibit caution in allocating innovation resources due to concerns regarding returns on investment and uncertainty about the outcomes of establishing relationships with new clients. Consequently, high switching costs may prompt suppliers to adopt a conservative approach toward innovation, potentially avoiding cutting-edge solutions to mitigate risks. In summary, the effect on physical resources predominantly arises from the imperative to safeguard psychological investments, while the impact on innovation resources is intricately linked to assessments of uncertainty and risk. Consequently, suppliers are predisposed to prioritize the preservation of existing relationships concerning physical resources while concurrently adopting a cautious stance when making determinations regarding innovation resource allocation. Based on this, we propose the following:

H4a: 

The higher the supplier-perceived switching cost, the stronger the willingness of supplier physical resource allocation.

H4b: 

The higher the supplier-perceived switching cost, the weaker the willingness of supplier innovation resource allocation.

3.3.4. Mediation Role of Supplier Value Perception

Supplier development initiatives, acting as external stimuli, serve multifaceted roles. Firstly, they signal to suppliers a buyer’s commitment to fostering collaboration, thereby accentuating the potential value inherent in their partnership [44,67]. When suppliers perceive a substantial value in their relationship with the buyer, they are inclined to channel their physical resources toward fulfilling a buyer’s requirements. This endeavor aims at fortifying and preserving the relationship, potentially leading to offerings of competitive pricing, flexible delivery services, and superior product quality [66]. Secondly, buyers extend support and resources to suppliers through collaborative developmental activities, fostering the cultivation of trust between both parties [5]. Trust encourages suppliers to invest physical resources in joint innovation and developmental endeavors, resulting in the provision of tailored, high-quality products and services to the buyer. Lastly, supplier development efforts may elevate perceived switching costs for suppliers, as adjustments to existing production processes, technologies, or resource allocations may be necessary to accommodate buyer requirements. When a supplier senses that cooperation with a specific buyer is terminated, the existing payment will become a sunk cost. In seeking to mitigate this perceived loss, suppliers may lean toward sustaining the collaboration, even if it deviates from the most rational decision-making approach. This tendency could manifest as a continued focus on existing technologies and production processes, thereby prioritizing a conservative allocation of resources to address potential uncertainties and risks associated with transformation efforts. In summary, we hypothesize the following:

H5a: 

Supplier-perceived relationship value positively mediates the relationship between supplier development and supplier physical resource allocation.

H5b: 

Supplier-perceived relationship trust positively mediates the relationship between supplier development and supplier physical resource allocation.

H5c: 

Supplier-perceived switching cost positively mediates the relationship between supplier development and supplier physical resource allocation.

Supplier development, originating from the buyer, signifies a buyer’s commitment to fostering a mutually beneficial relationship with a supplier. This commitment extends to shared market opportunities, strategic collaborations, and other cooperative endeavors, emphasizing the relational aspect of their engagement [53]. When suppliers recognize the value embedded within the buyer–supplier relationship, they are more inclined to allocate resources toward innovation initiatives. Such initiatives may include the development of novel products, the provision of innovative solutions tailored to a buyer’s future requirements, and other proactive endeavors aimed at enhancing mutual benefit [71]. Additionally, through supplier development, the buyer communicates signals of collaboration, support, and mutual growth, thereby fostering trust. This perceived trust cultivates a culture of joint innovation efforts, encouraging suppliers to actively engage in resource allocation for innovation purposes [73]. This engagement may involve sharing sensitive information, co-investing in research and development projects, and participating more openly in the innovation process [9]. Finally, supplier involvement in development projects often necessitates technological upgrades, adjustments to production processes, or the reallocation of resources. Suppliers’ perceptions of these transition costs may evoke concerns regarding risks and uncertainties associated with relationship transitions. High perceived transition costs can potentially impede suppliers’ proactive commitment to innovation [74]. Consequently, suppliers may adopt a cautious stance toward innovation, prioritizing existing technologies and solutions to mitigate uncertainty and risk in the innovation process. In summary, we hypothesize the following:

H6a: 

Supplier-perceived relationship value positively mediates the relationship between supplier development and supplier innovation resource allocation.

H6b: 

Supplier-perceived relationship trust positively mediates the relationship between supplier development and supplier innovation resource allocation.

H6c: 

Supplier-perceived switching cost positively mediates the relationship between supplier development and supplier innovation resource allocation.

3.3.5. The Moderating Effect of Supplier-Perceived Relationship Trust

It has been established that behaviors become interdependent in situations where one party must persuade the other to engage in actions aimed at achieving mutual objectives [75]. Social exchange theory underscores the reciprocal nature of relationships, wherein individuals seek to maximize benefits through exchanges [76]. Central to this theory is the concept of relationship trust, which is a critical form of social capital that fosters cooperation and reciprocity in interactions. High levels of relationship trust between buyers and suppliers lead to greater willingness to share valuable resources, as trust mitigates perceived risks and enhances collaboration [77]. Therefore, we introduce supplier-perceived relationship trust as a moderating factor to elucidate how trust levels influence resource sharing motivation and other supplier value perceptions.

When suppliers perceive high relationship value with a buyer, it signifies a strategic, long-term collaboration rather than a simple transaction [78]. Supported by high-level relationship trust, suppliers are inclined to proactively adjust physical resource allocation [79], investing in enhancing production efficiency, quality control, and flexibility in responding to the buyer’s changing demands [80]. Conversely, in low-trust scenarios, suppliers may maintain existing resource allocations to mitigate risks, prioritizing short-term gains over large-scale investments. Regarding innovation resources, high-level relationship trust encourages suppliers to invest in collaborative development, sharing innovative ideas, and actively participating in new projects [81]. This trust forms a robust foundation for deep collaboration, enhancing suppliers’ flexibility in allocating innovation resources and their willingness to invest in common innovation goals. Moreover, it reduces the buyer’s need for additional efforts, as suppliers are more inclined to proactively support the buyer’s innovation objectives within this collaborative framework. In conclusion, we assume the following:

H7a: 

Under high supplier-perceived relationship trust, the positive mediation role of supplier-perceived relationship value between supplier development and supplier physical resource allocation will be enhanced.

H7b: 

Under high supplier-perceived relationship trust, the positive mediation role of supplier-perceived relationship value between supplier development and supplier innovation resource allocation will be enhanced.

In the domain of supplier development, perceived relationship trust emerges as a critical moderator shaping how suppliers navigate the perceived switching costs associated with resource allocation. A robust perception of relationship trust imbues suppliers with heightened confidence in a buyer’s commitment, mitigating apprehensions regarding opportunistic behavior or contract terminations during collaborative endeavors [72]. Despite encountering substantial switching costs, elevated levels of trust assuage uncertainties spanning purchase prices and payment terms, fostering suppliers’ willingness to furnish tangible resources to existing buyers [2,74]. Moreover, supplier-perceived relationship trust exerts a favorable regulatory influence on the impact of supplier development initiatives on innovative resource allocation, attenuating the adverse effects of perceived switching costs on suppliers’ allocation decisions [82]. This trust engenders a psychological contract. The collaboration between buyers and suppliers transcends mere economic considerations, constituting a strategic and enduring investment [82]. Such trust-based relationships not only catalyze positive collaborative endeavors but also afford suppliers a steadfast psychological disposition, compelling them to make innovation-driven resource allocation decisions that accrue benefits to both themselves and buyers. In conclusion, we propose the following:

H8a: 

Under high supplier-perceived relationship trust, the positive mediation role of supplier-perceived switching cost between supplier development and supplier physical resource allocation will be enhanced.

H8b: 

Under high supplier-perceived relationship trust, the negative mediation role of supplier-perceived switching cost between supplier development and supplier innovation resource allocation will be weakened.

4. Research Methodology

4.1. Questionnaire Design

We conducted a comprehensive literature review to identify pertinent variables, which were predominantly sourced from international contexts. Recognizing the necessity for adapting these variables to the Chinese context, we conducted field visits to ascertain differences among Chinese suppliers in resource allocation, encompassing both physical and innovation resources. Utilizing translation and reverse translation methodologies, we developed a Chinese version of the questionnaire, which was initially piloted in Shanxi Province. Subsequent revisions were informed by feedback from industry practitioners and academic experts, culminating in a final version tailored for large-scale testing. Each item was assessed using a five-point Likert scale with responses ranging from “completely disagree” (1) to “completely agree” (5).

Supplier development, aimed at enhancing supplier capability or performance, has predominantly been studied from the buyer’s perspective [14,67,68,69]. This study shifts the focus to the supplier’s viewpoint, particularly in assessing perceptions of production materials, energy, and time during the development process, which is consistent with Jääskeläinen et al. (2022) [54]. We refine and extend existing conceptualizations, particularly regarding supplier value perception, which encompasses relationship value, trust, and switching costs. Tescari and Brito (2016) approached value creation in the buyer–supplier relationship from a binary perspective, emphasizing practical aspects like reliability, flexibility, cost savings, and learning enhancement [83]. However, their focus was primarily on potential value from customers expanding existing business, overlooking broader sources of value. In contrast, Qiao et al. (2022) consider supplier perceived relationship attractiveness, encompassing economic expectations and potential value from new business development, market expansion, and innovation enhancement, aligning with our study’s innovation resource considerations [16]. Hence, we adopt their approach to measure supplier-perceived relationship value. Regarding supplier-relationship perceived trust, while most research is buyer-centric [30,42,43], our study incorporates the supplier’s perspective [16,84,85] and explores loyalty, support, shared values, fairness, and reliability, aligning closely with Hald, Cordón, and Vollmann (2009) [33]. We broaden the research scope to include switching costs, which is a factor often overlooked in studies focusing on preferred customer status from the buyer’s perspective [57,86,87]. Consistent with Geiger et al. (2012) [56], we adopt their items, maintaining a supplier-centric perspective specific to the buyer–supplier relationship. Our study distinguishes between physical and innovation resource allocation, following Pulles et al. (2014) [14], who offer a comprehensive framework encompassing extreme situations, professional contact, and time investment in new product development.

Meanwhile, we also considered two control variables. Due to variations in supplier participation and the timing of establishing contact with the buyer in the supplier development project, suppliers may have different perceptions of the buyer, impacting their resource allocation decisions. Therefore, we included the length of the buyer–supplier relationship as a control variable. Additionally, our study focused on the perception of specific buyer–supplier relationships within the supplier development project and did not consider supplier characteristics. However, supplier size influences the volume of physical and innovation resources, affecting allocation decisions. To account for these effects, we controlled for the length of the buyer–supplier relationship and firm size, following the approach of Vos et al. (2016) [37].

4.2. Sample and Data Collection

China’s manufacturing industry, known for its formidable production capabilities, has shown resilience amidst the global pandemic, evolving from a focus solely on manufacturing to integrating innovation. Suppliers in China now not only provide essential raw materials like steel and machinery but also emphasize developing advanced technologies such as power systems, new energy fuel cells, and chips. Leveraging China’s manufacturing expertise, we selected suppliers with both physical and innovative resources for our investigation. Initially, we systematically sampled 30 manufacturers from Shaanxi’s manufacturing directory, conducting background research and telephone interviews to ensure their suitability. Subsequently, we began with a pool of 22 manufacturing enterprises, initiating the snowball sampling method to expand our sample size and capture a broader spectrum of suppliers with significant physical and innovation resources. This approach allowed us to capture a diverse range of suppliers across different industries and geographical locations, ensuring the breadth and depth of our research findings. In our survey, we targeted middle and senior managers directly involved in supplier development projects, as they possess valuable insights into resource allocation decisions. We distributed questionnaires both in paper form and via email, ensuring clarity regarding the criteria for participation and screening for suitable respondents who could provide insights into both physical and innovation resources. Additionally, we included specific questions in the questionnaire to verify the respondents’ suitability, such as their ability to supply scarce raw materials/parts and contribute new ideas or technologies to the buyer. Furthermore, to validate the authenticity of the responses and maintain data integrity, we conducted systematic sampling visits to some respondents to confirm their identities and ensure the accuracy of their feedback. In total, we distributed 700 questionnaires, yielding 246 valid responses after meticulous screening, resulting in a response rate of 35.14% (see

Table 2. Firm profiles and informant profiles.

Characteristics of Firm			Characteristics of Respondents
1. Length of buyer–supplier relationship	Freq	%	1. Position of the respondent	Freq	%
Less than 3 years	15	6.10	R&D department staff	103	40.20
3–5 years	27	11.00	Sales representative	72	29.30
5–10 years	33	13.40	Customer maintenance personnel	36	14.60
10–15 years	66	26.80	Product manager	12	4.90
More than 15 years	105	42.70	Others involved in supplier development	27	11.00
2. Firm size	Freq	%	2. Tenure of respondent in this position	Freq	%
Less than 500 employees	9	3.70	Less than 3 years	18	7.30
500–2000 employees	63	25.60	3–5 years	45	18.30
2000–5000 employees	78	31.70	5–10 years	69	28.00
5000–10,000 employees	69	28.00	10–15 years	72	29.30
More than 10,000 employees	27	11.00	More than 15 years	42	17.10
3. Firmtype	Freq	%	3. Length of respondent involvement in	Freq	%
Metal products, mechanical and equipment manufacturing	60	24.40	focal buyer–supplier relationship
Computer and other electronic equipment manufacturing	54	22.00	Less than 3 years	30	12.20
Automotive manufacturing	42	17.10	3–5 years	48	19.50
Home appliance manufacturing	33	13.40	5–10 years	75	30.50
Chemical raw materials and products manufacturing	48	19.50	10–15 years	66	26.80
Other manufacturing	9	3.70	More than 15 years	27	11.00

).

4.3. Nonresponse Bias and Common Method Bias

According to the method proposed by Armstrong and Overton (1977) [88], we conducted t-tests to compare descriptive differences in collected data between early and late periods. Results indicated no significant disparities in firm size (p = 0.287), firm type (p = 0.336), tenure of respondent in their position (p = 0.375), length of respondent involvement in the focal buyer–supplier relationship (p = 0.228), and respondent position (p = 0.125). To address nonresponse bias, we gathered demographic information from participants who agreed but did not complete the survey [89]. T-test results showed no statistical differences between respondents and nonrespondents in firm size (p = 0.261), firm type (p = 0.382), tenure (p = 0.343), length in the relationship (p = 0.185), and respondent position (p = 0.137), alleviating concerns regarding nonresponse bias. Additionally, to mitigate common method bias due to respondents completing the same questionnaire, we conducted the Harman single-factor test, revealing nine factors with eigenvalues above 1 and an unrotated maximum factor explaining only 28.141% of the total variance (<40%). Furthermore, combining first-order latent factor control methods, adding a common methodological bias to the six-factor model yielded no significant differences in metrics compared to the original model (

Table 3. Controlling for effects of an unmeasured latent methods factor method.

Model	χ2	df	χ2/df	CFI	TLI	IFI	RMSEA
Six-factor model	129.658	99	1.310	0.948	0.937	0.950	0.062
Six-factor model with common method factor	128.523	98	1.311	0.947	0.937	0.950	0.062

). In summary, nonresponse variance and common method bias were deemed acceptable.

4.4. Reliability and Validity

We employed a two-step method to assess reliability [90]. Firstly, we conducted exploratory factor analysis (EFA) for each construct to ensure unidimensionality. Subsequently, we calculated Cronbach’s alpha and composite reliability. All values exceeded 0.7, indicating the reliability of these variables (see

Table 4. Measurement item properties.

Constructs and Items	Loading	CR	AVE
Supplier development (SD) (Cronbach’s α = 0.833)
We think this customer has provided high expertise to us, such as rich experience or know-how.	0.664	0.836	0.506
We think this customer has provided abundant resources to us, such as equipment or tools.	0.694
We think this customer has helped us a lot to become a better supplier, such as providing training or service.	0.679
We think this customer has initiated programs that are desired to enhance our overall business, such as delivery, product quality or innovation performance.	0.724
Supplier-perceived relationship value (SPRV) (Cronbach’s α = 0.852)
Compared to our other customers,
Our relationship with this customer will help us to remain competitive in pricing.	0.649	0.861	0.513
Our relationship with this customer will help us to reduce costs.	0.662
Our relationship with this customer will help us to make high profits.	0.712
Our relationship with this customer will help us to expand our existing business and market.	0.885
Our relationship with this customer will help us to develop new businesses and markets.	0.778
Our relationship with this customer will contribute to our innovation ability.	0.570
Supplier-perceived relationship trust (SPRT) (Cronbach’s α = 0.859)
Compared to our other customers,
We believe this customer would not behave opportunistically even if they had a chance.	0.782	0.866	0.520
We believe this customer would give us “free assistance” when we need.	0.700
We believe this customer would have consistent beliefs about behaviors, goals and policies with us.	0.672
We believe this customer would have a fair distribution of the benefits and costs.	0.705
We believe this customer would propose reasonable requirements and help us to seek joint alternative solutions.	0.770
We believe this customer would fulfill the promises and commitments.	0.690
Supplier-perceived switching cost (SPSC) (Cronbach’s α = 0.802)
We think the sum of disadvantages associated with a potential switch to another customer is probably very high.	0.768	0.811	0.520
We think our company would lose a lot by switching to another customer.	0.730
We think the costs (time, effort and money) to switch to another relationship would be very high.	0.792
We think the barriers to terminating the current relationship and establishing an alternative relationship would be very high.	0.576
Physical resources (PS) (Cronbach’s α = 0.806)
Compared to our other customers,
We grant this customer better utilization of our production facilities	0.599	0.813	0.526
We choose to give this customer priority in the allocation of our products in the case of extreme events (e.g., natural disasters)	0.874
We allocate our scarce materials to this customer in case of capacity bottlenecks.	0.702
We dedicate more specialized equipment to the relationship with this customer.	0.699
Innovation resources (IRs) (Cronbach’s α = 0.811)
Compared to our other customers,
We are more willing to share key technological information with this customer	0.730	0.821	0.534
We share our best ideas with this customer first	0.724
We dedicate more innovation resources to the relationship with this customer.	0.752
We spend more of our product development time on projects of this customer.	0.716

).

We assessed convergence validity by calculating covariance. Firstly, a confirmatory factor analysis (CFA) model of the three first-order factors of supplier relationship perception was conducted, yielding model fit indices χ² (df = 99) = 129.658, RMESA = 0.062, CFI = 0.948, TLI = 0.937, IFI = 0.950. Subsequently, a CFA model incorporating all latent variables was run, treating supplier relationship perception as a second-order factor with three summated indicators of the first-order factors. The model fit indices χ² (df = 103) = 239.012, RMESA = 0.128, CFI = 0.769, TLI = 0.730, IFI = 0.775. The three-factor model demonstrated significantly better fit than the two-factor model, indicating superior discriminatory validity [91]. Additionally, no significant common methodological bias was observed. Moreover, all items in the original model exhibited normalized factor loads exceeding 0.50 and significance at the 0.01 level (see Table 4), further supporting convergent validity [92]. Furthermore, comparing the square root of extracted mean variance with correlation coefficients confirmed discriminant validity, with all values surpassing the correlation coefficient between core constructs and other constructs (see

Table 5. Means, standard deviations, correlations, reliability and validity.

	1	2	3	4	5	6	7	8
Physical resources	0.725
Innovation resources	0.673 ***	0.731
Supplier development	0.370 ***	0.339 ***	0.712
Supplier-perceived relationship value	0.698 ***	0.546 ***	0.329 ***	0.716
Supplier-perceived relationship trust	0.586 ***	0.520 ***	0.374 ***	0.593 ***	0.721
Supplier-perceived switching cost	0.473 ***	0.024	0.289 **	0.349 ***	0.194 *	0.721
Length of buyer-supplier relationship	0.285 **	0.268 **	0.173	0.106	0.013	0.063
Firm size	0.275 **	0.122	−0.042	0.089	0.049	0.282	0.212
Mean	16.037	15.122	19.732	23.207	23.451	14.366	3.890	3.170
SD	2.0273	2.622	3.174	4.106	3.739	2.870	1.247	1.052

Note(s): Numbers on the diagonal are the square roots of the AVE values. * p < 0.05; ** p < 0.01; *** p < 0.001.

).

4.5. Hypothesis Testing

Our analysis, conducted using SPSS version 25.0, employed Variance Inflation Factor (VIF) diagnostics, indicating negligible collinearity concerns with all values below 3.0. Leveraging the ‘process’ plugin developed by Hayes (2012) [93], capable of handling concurrent mediation and moderation effects, proved suitable for our investigation. Our findings, as presented in

Table 6. Direct effect 1.

	Supplier-Perceived Relationship Value					Supplier-Perceived Relationship Trust					Supplier-Perceived Switching Cost
	coeff	se	t	LLCI	ULCI	coeff	se	t	LLCI	ULCI	coeff	se	t	LLCI	ULCI
Constant	13.2689	3.1532	4.2080	6.9913	19.5465	14.3071	2.8230	5.0680	8.6868	19.9274	6.6630	2.1365	3.1187	2.4096	10.9164
Length of buyer-supplier relationship	0.0934	0.3642	0.2563	−0.6318	0.8185	−0.2138	0.3261	−0.6555	−0.8630	0.4355	−0.1285	0.2468	−0.5206	−0.6198	0.3628
Firm size	0.3768	0.4258	0.8851	−0.4708	1.2245	0.2864	0.3812	0.7514	−0.4724	1.0453	0.8363	0.2885	2.8988 **	0.2619	1.4106
Supplier development	0.4247	0.1400	3.0338 **	0.1460	0.7034	0.4595	0.1253	3.6665 ***	0.2100	0.7091	0.2813	0.0949	2.9659 **	0.0925	0.4702
R2	0.1197					0.1491					0.1727
F	3.5349					4.5554					5.4271

Note(s): ** p < 0.01; *** p < 0.001.

, substantiate that supplier development significantly fosters supplier-perceived relationship value, trust, and switching costs (H1a, H1b, and H1c, respectively). Moreover, after controlling for buyer–supplier relationship duration and firm size (see

Table 7. Direct effect 2.

	Physical Resources						Innovation Resources
	coeff	se	t	LLCI	ULCI	coeff	se	t	LLCI	ULCI
Constant	8.9888	1.4390	6.2466	6.1240	11.8537	7.7454	1.9566	3.9585	3.8500	11.6408
Length of buyer-supplier relationship	0.2767	0.1662	1.6643	−0.0543	0.6076	0.4097	0.2260	1.8128	−0.0403	0.8597
Firm size	0.4885	0.1943	2.5141 *	0.1017	0.8753	0.2336	0.2642	0.8842	−0.2924	0.7596
Supplier development	0.2241	0.0639	3.5083 ***	0.0969	0.3513	0.2555	0.0869	2.9415 **	0.0826	0.4285
R2	0.2480					0.1687
F	8.5734					5.2771

Note(s): * p < 0.05; ** p < 0.01; *** p < 0.001.

), supplier development exhibits a significant positive influence on both physical and innovation resources. However, upon introducing the three mediators, the direct impact of supplier development on these resources loses significance, suggesting a mediating effect. Further examination (see

Table 8. Mediation model.

	Physical Resources						Innovation Resources
	coeff	se	t	LLCI	ULCI	coeff	se	t	LLCI	ULCI
Constant	3.1262	1.1915	2.6239	0.7527	5.4997	3.2496	1.9203	1.6923	−0.5758	7.0750
Length of buyer-supplier relationship	0.3088	0.1157	2.6692 **	0.0783	0.5393	0.3968	0.1865	2.1277 *	0.0253	0.7683
Firm size	0.2409	0.1413	1.7048	−0.0406	0.5225	0.2787	0.2278	1.2234	−0.1751	0.7325
Supplier development	0.0259	0.0497	0.5206	−0.0731	0.1248	0.1271	0.0800	1.5881	−0.0323	0.2866
Supplier-perceived relationship value	0.2051	0.0438	4.6804 ***	0.1178	0.2925	0.2516	0.0706	3.5620 ***	0.1109	0.3924
Supplier-perceived switching cost	0.1527	0.0547	2.7915 **	0.0437	0.2618	−0.2320	0.0882	−2.6308 *	−0.4077	−0.0563
Supplier-perceived relationship trust	0.1484	0.0474	3.1330 **	0.0540	0.2427	0.1889	0.0763	2.4750 *	0.0369	0.3410
R2	0.6559					0.4656
F	23.8280					3.9672

Note(s): * p < 0.05; ** p < 0.01; *** p < 0.001.

) reveals significant positive associations between supplier-perceived relationship value, trust, and switching costs with physical resources, affirming assumptions H2a, H3a, and H4a. Similarly, supplier-perceived relationship value and trust positively influence innovation resources (H2b, H3b), while supplier-perceived switching costs exert a negative impact (H4b).

Upon the simultaneous inclusion of the three variables as mediators in the model, the 95% confidence intervals for Mediations 1, 2, 3, 4, and 6 were determined to be [0.0140, 0.0845], [0.0062, 0.0709], [0.0024, 0.0501], [0.0264, 0.2377], and [−0.1792, −0.0039], respectively. Notably, none of these intervals encompassed the coefficient 0, affirming hypotheses H5a, H5b, H5c, H6a, and H6c. Conversely, for Mediation 5, the 95% confidence interval [−0.0126, 0.2258] encompassed the coefficient 0, thereby indicating that H6b did not attain significance. Furthermore, we conducted a comparative analysis of the effect ratios of each mediator across different outcome variables, specifically physical and innovation resources (see

Table 9. The analysis of mediation effect.

	Effect	BootSE	BootLLCI	BootULCI	Ratio
Total effect 1	0.0978	0.0266	0.0499	0.1530	88.49%
Mediation 1 (Supplier development → Supplier-perceived relationship value → Physical resources)	0.0430	0.0179	0.0140	0.0845	38.87%
Mediation 2 (Supplier development → Supplier-perceived relationship trust → Physical resources)	0.0336	0.0169	0.0062	0.0709	30.43%
Mediation 3 (Supplier development → Supplier-perceived switching cost → Physical resources)	0.0212	0.0123	0.0024	0.0501	19.19%
Total effect 2	0.1284	0.0634	0.0100	0.2612	50.25%
Mediation 4 (Supplier development → Supplier-perceived relationship value → Innovation resources)	0.1069	0.0554	0.0264	0.2377	41.84%
Mediation 5 (Supplier development → Supplier-perceived relationship trust → Innovation resources)	0.0868	0.0604	−0.0126	0.2258	33.97%
Mediation 6 (Supplier development → Supplier-perceived switching cost → Innovation resources)	−0.0653	0.0470	−0.1792	−0.0039	−25.56%

). Notably, the effect ratio of Mediation 1 (38.87%) was surpassed by that of Mediation 4 (41.84%), while the effect ratio of Mediation 2 (30.43%) trailed that of Mediation 5 (33.97%). Consequently, H2c lacks support, whereas H3c was substantiated.

We employed bootstrapping techniques to scrutinize moderated mediation effects. This is mainly because bootstrapping can enhance the robustness of model testing through repeated sampling, and it includes many models capable of simultaneously handling mediation and moderation effects [94].

Table 10. Moderated mediation.

	Physical Resources						Innovation Resources
	coeff	se	t	LLCI	ULCI	coeff	se	t	LLCI	ULCI
Constant	13.2788	1.0740	12.3643	11.1384	15.4192	9.7589	1.7010	5.7373	6.3689	13.1490
Length of buyer–supplier relationship	0.3496	0.1106	3.1602 **	0.1291	0.5700	0.4637	0.1752	2.6470 **	0.1146	0.8129
Firm size	0.2231	0.1349	1.6535	−0.0458	0.4920	0.2245	0.2137	1.0504	−0.2014	0.6504
Supplier development	0.0273	0.0472	0.5780	−0.0668	0.1213	0.1265	0.0747	1.6923	−0.0225	0.2754
Supplier-perceived relationship value	0.2078	0.0431	4.8223 ***	0.1219	0.2937	0.2768	0.0683	4.0559 ***	0.1408	0.4128
Supplier-perceived switching cost	0.1951	0.0556	3.5081 ***	0.0843	0.3059	−0.1872	0.0881	−2.1259 *	−0.3628	−0.0117
Supplier-perceived relationship trust	0.1385	0.0451	3.0693 **	0.0486	0.2285	0.1763	0.0715	2.4666 *	0.0339	0.3188
Supplier-perceived relationship value × trust	0.0094	0.0079	1.1871	−0.0064	0.0252	0.0297	0.0126	2.3625 *	0.0046	0.0547
Supplier-perceived switching cost × trust	0.0330	0.0130	2.5283 *	0.0070	0.0590	0.0414	0.0207	2.0036 *	0.0002	0.0826
R2	0.6981					0.5471
F	21.0958					11.0248

Note(s): * p < 0.05; ** p < 0.01; *** p < 0.001.

reveals that while supplier-perceived relationship trust moderates, supplier-perceived relationship value positively influences physical resources. However, the interactive effect of supplier-perceived relationship value and trust does not significantly impact physical resources, thus confirming H1a and H2a but not supporting H7a. Furthermore, the analyses depicted in Figure 2 and

Table 11. The results of indirect effect (supplier-perceived relationship trust as the moderator).

		Index	Effect	BootSE	BootLLCI	BootULCI
Moderated mediation 1 (Supplier development → Supplier-perceived relationship value → Physical resources)	eff1(M – 1SD)	−3.7389	0.0733	0.0347	0.0111	0.1481
	eff2(M)	0	0.0883	0.0370	0.0267	0.1709
	eff3(M + 1SD)	3.7389	0.1032	0.0461	0.0336	0.2118
Moderated mediation 2 (Supplier development → Supplier-perceived switching cost → Physical resources)	eff1(M – 1SD)	−3.7389	0.0202	0.0265	−0.0321	0.0758
	eff2(M)	0	0.0549	0.0330	0.0062	0.1331
	eff3(M + 1SD)	3.7389	0.0896	0.0513	0.0124	0.2070
Moderated mediation 3 (Supplier development → Supplier-perceived relationship value → Innovation resources)	eff1(M – 1SD)	−3.7389	0.0705	0.0420	0.0017	0.1608
	eff2(M)	0	0.1176	0.0557	0.0301	0.2455
	eff3(M + 1SD)	3.7389	0.1647	0.0799	0.0409	0.3515
Moderated mediation 4 (Supplier development → Supplier-perceived switching cost → Innovation resources)	eff1(M – 1SD)	−3.7389	−0.0962	0.0573	−0.2265	−0.0063
	eff2(M)	0	−0.0527	0.0410	−0.1552	0
	eff3(M + 1SD)	3.7389	−0.0091	0.0437	−0.1185	0.0626

and

Table 12. The index of moderated mediation (supplier-perceived relationship trust as the moderator).

	Index	BootSE	BootLLCI	BootULCI
Moderated mediation 1 (Supplier development → Supplier-perceived relationship value → Physical resources)	0.0040	0.0046	−0.0011	0.0164
Moderated mediation 2 (Supplier development → Supplier-perceived switching cost → Physical resources)	0.0093	0.0064	0.0002	0.0250
Moderated mediation 3 (Supplier development → Supplier-perceived relationship value → Innovation resources)	0.0126	0.0084	0.0010	0.0332
Moderated mediation 4 (Supplier development → Supplier-perceived switching cost → Innovation resources)	0.0116	0.0081	−0.0016	0.0292

indicate that supplier development significantly influences physical resources through supplier-perceived relationship value in both low and high levels of supplier-perceived relationship trust without the latter playing a moderating role. In parallel, Table 10 indicates that with supplier-perceived relationship trust as a moderator, the supplier-perceived switching cost positively impacts physical resources, and the interaction of supplier-perceived switching cost and trust significantly boosts physical resources, confirming H1c and H4a while supporting H8a. Similarly, examinations from Figure 2 and Table 11 and Table 12 demonstrate that supplier development notably impacts physical resources through supplier-perceived switching cost in the high supplier-perceived relationship trust group. Moreover, supplier-perceived relationship value positively affects innovation resources, and its interaction with supplier-perceived relationship trust enhances innovation resources. When trust moderates, supplier development significantly affects innovation resources through the supplier-perceived relationship value across both low and high trust levels, reaffirming H1a and H2b while supporting H7b. Incorporating moderated mediation analyses from Figure 2 and Table 11 and Table 12, supplier development significantly influences innovation resources via supplier-perceived relationship value across varying levels of supplier-perceived relationship trust. Furthermore, supplier-perceived switching cost detrimentally impacts innovation resources, while its interaction with supplier-perceived relationship trust yields a favorable effect on innovation resources. This reaffirms the validation of hypotheses H1c and H4b, thereby supporting H8b. Moreover, within the low supplier-perceived relationship trust group, supplier development notably impacts innovation resources through the mechanism of supplier-perceived switching cost.

When examining the relationship between supplier development as the independent variable and physical resources and innovation resources as the dependent variables, the inclusion of the length of the buyer–supplier relationship as a control variable does not yield significant impact. This indicates that supplier development’s direct impact on physical and innovation resources is mainly driven by the benefits received by the supplier from the project irrespective of the buyer–supplier relationship duration. In contrast, firm size significantly correlates with greater physical resource abundance, highlighting larger firms’ tendency to possess more resources. However, larger firms do not always show a similar increase in innovative technology patents compared to smaller ones in the same industry. This disparity in resource volumes highlights differing influences on resource allocation decisions: while resource-rich firms can cater to buyer needs comprehensively, those with limited resources face greater challenges in allocation. Furthermore, both the length of the buyer–supplier relationship and firm size exhibit significant impacts on physical and innovation resources in the mediation and moderated mediation models. This underscores the importance of long-standing cooperation in fostering mutual understanding and informed resource allocation decisions. In summary, controlling for variables such as firm size and the length of the buyer–supplier relationship is imperative. This ensures a nuanced understanding of the dynamics influencing resource allocation decisions and mitigates the potential biases arising from variations in firm characteristics and relationship durations.

5. Conclusions and Implications

5.1. Theoretical Contributions

This paper adds to a body of literature highlighting the significance of perceptions in supply chain management research [16,18]. It investigates how supplier development activities influence supplier resource allocation behaviors, shedding light on the psychological decision-making processes of suppliers.

Firstly, we establish the mediating mechanism between supplier development and resource allocation by delving into the inner motivations of supplier decision making. Our study reveals that supplier-perceived relationship value, trust, and switching costs serve as mediators in this process. While prior research has explored the direct impact of supplier-specific investments, akin to supplier development, on resource allocation [2], such investments facilitate suppliers in enhancing their capabilities and establishing positive relationships, thereby prompting resource allocation behaviors. Hence, there remains a necessity to delve deeper into the mediating pathways between supplier development and resource allocation; however, existing studies have overlooked this influencing mechanism. Therefore, we utilize the S-O-R framework to further advance existing research by demonstrating the mediating roles of supplier-perceived relationship value, trust, and switching costs. These findings resonate with psychological expectancy theory, relational perspectives, and psychological investment theory, respectively. Notably, our study addresses the oversight of negative emotions associated with supplier resource allocation behaviors, drawing upon behavioral investment theory to illuminate the passive element perceived by suppliers—the negative emotions induced by switching costs. Furthermore, considering the distinct characteristics of physical and innovation resources, we differentiate supplier value preferences during allocation and examine the varied mediating effects. For physical resources, suppliers prioritize the actual and potential economic value offered by buyers, with supplier-perceived relationship value dominating among the mediators, all yielding positive effects. In contrast, for innovation resources, supplier-perceived relationship value exhibits significant positive mediation, while supplier-perceived switching costs contribute to significant negative mediation, diverging from the dynamics observed with physical resources. Given the adverse impact of switching costs, the influence ratio of supplier-perceived relationship value and trust in innovation resources slightly exceeds that observed with physical resources. Consequently, our study identifies distinct mechanisms guiding value judgments among suppliers when allocating different resource types.

Secondly, this study examines the interdependence between buyers and suppliers, considering varying levels of supplier-perceived trust and their impact on mediations. Previous research has examined the impact of supplier-specific investments on supplier resource allocation with a primary focus on supplier dependence as a moderator, considering factors related to power [2]; however, based on social exchange theory, trust in buyer–supplier relationships serves as a vital bond that solidifies the relationship between both parties, and its impact cannot be overlooked. Building upon this gap, we investigate supplier-perceived trust as a moderating variable. This study uniquely integrates trust as both a mediator and moderator, which is a novel approach not previously explored in supplier resource allocation studies. Our findings reveal that when “physical resources” are the outcome variables, supplier-perceived relationship trust moderates supplier-perceived switching costs. Conversely, when “innovation resources” is the outcome variable, supplier-perceived relationship trust moderates supplier-perceived relationship value. To validate the appropriateness of trust as a moderator, we separately examine its effects on supplier-perceived relationship value and switching costs while keeping other variables constant, confirming our assumptions. This validation underscores the differential impact of supplier-perceived relationship trust as a boundary condition on other mediators. By incorporating trust as a moderating variable, our study extends social exchange theory’s applicability and enhances our understanding of relational trust dynamics. This moderating role not only elucidates why trust exerts varying effects on resource sharing in different contexts but also offers practical insights for relationship management in business and organizational settings.

Lastly, we employ the S-O-R framework to elucidate how supplier development influences resource allocation from a supplier’s psychological perspective, expanding the applicability of the S-O-R framework. Past research on supplier development has focused solely on performance outcomes, overlooking the substantial decisions regarding the upstream supplier resource allocation necessary to realize these competitive advantages. However, existing studies have neglected the psychological motivations behind suppliers’ implementation of allocation behaviors. Understanding this decision-making process is crucial for buyers to achieve higher levels of performance advantage. To address this gap, we introduce the S-O-R theory, which allows for a nuanced understanding of how suppliers evaluate external stimuli and make resource allocation decisions based on inner value assessments, thereby extending the application of the S-O-R framework in the buyer–supplier relationship management domain.

5.2. Managerial Implications

First of all, our study underscores the importance of supplier development activities in enhancing suppliers’ perceptions of relationship value, trust, and switching costs, providing critical managerial insights. Firstly, effective supplier development activities should be implemented, such as establishing clear cooperation agreements and contracts specifying delivery deadlines, quality standards, pricing terms, etc., or providing technical support and knowledge transfer to help suppliers improve their production technology and management capabilities, thus forming clear value expectations for suppliers. Secondly, buyers can also share strategic goals and development plans with suppliers, establish open and transparent communication channels, promptly share critical information and market changes, and demonstrate stability in cooperation by fulfilling commitments, resolving issues promptly during the collaboration process and thereby enhancing suppliers’ trust in specific buyers. Thirdly, when engaging in joint research and development and innovation projects with suppliers, attention should be paid to protecting innovation outcomes and intellectual property rights, increasing the barriers for suppliers to exit the partnership, and enhancing suppliers’ perceived switching costs.

Secondly, our study highlights the role of suppliers’ psychological perceptions in prioritizing different resource allocations. Suppliers’ willingness to allocate physical and innovation resources is enhanced by their expectations of growth opportunities, skill enhancement values derived from buyer–supplier relationships, and emotional dependencies such as commitments, strong connections, and satisfaction in trust-building aspects. Therefore, buyers can provide training programs and development opportunities to help suppliers improve management capabilities and skills. Buyers can also commit to establishing stable partnerships with suppliers by signing long-term supply contracts or agreements that prioritize suppliers, thereby fostering suppliers’ willingness to prioritize resource allocation; however, compared to physical resources, enhancing relationship value and trust requires more effort to obtain innovation resources. At the same time, buyers can customize products or services to better meet specific buyer needs and specifications. They can also secure exclusive rights to relevant patents, technologies, or other intellectual property, or control critical aspects of the supply chain through vertical integration, such as raw material procurement, production processes, or distribution channels. This ensures control over key resources and capabilities throughout the value chain, thereby increasing suppliers’ perceived switching costs and enhancing their willingness to prioritize material resource allocation. Efforts in these areas may need to be reduced if buyers seek to obtain innovation resources.

Lastly, buyers must recognize the significant impact of supplier-perceived relationship trust on resource allocation. When buyers aim to prioritize access to supplier resources through supplier development activities, measures can be taken to enhance suppliers’ perception of trust to reduce efforts related to relationship value and switching costs, such as sharing market trends, technological innovations, demand forecasts, and other information with suppliers to help them better adjust production and supply chain strategies; establishing solid partnerships and closely collaborating with key suppliers to jointly develop markets, innovative products, or services; establishing open, timely, and transparent communication channels to share information, requirements, and decision-making processes with suppliers; ensuring consistency and accuracy in communication to avoid information asymmetry and misunderstandings; and strictly adhering to contract terms and commitments, including payment conditions, delivery deadlines, quality standards, etc., demonstrating a buyer’s credibility and reliability.

5.3. Limitations and Future Research Opportunities

This study, grounded in the S-O-R theoretical framework, elucidates why supplier development prompts suppliers to prioritize resources, substantiating their perceived value judgments. Nonetheless, certain limitations warrant acknowledgment. Firstly, the study exclusively examines the influence of suppliers’ value perception and trust moderation on resource allocation decisions, albeit acknowledging the multifaceted nature of such determinants. Future inquiries should delve into additional factors such as distributive, procedural, and interactional justice, as well as power dynamics and firm size, to comprehensively understand supplier-perceived value. Secondly, the study’s reliance on cross-sectional data fails to capture changes in supplier value perceptions over time. Future research should consider longitudinal data collection to track evolving perceptions throughout the supplier relationship lifecycle. Lastly, the study’s sole focus on supplier perspectives neglects a buyer’s value perception. Future investigations should adopt a dual perspective to compare and contrast both parties’ perceptions, offering insights into bilateral interests and underlying rationales.