1. Introduction
The emergence of the COVID-19 pandemic has further underscored the importance of supply chain security, making it a significant topic of research in recent years. Countries around the world are striving to devise and implement a series of policy measures to ensure supply chain security or to mitigate the potential negative impacts of supply chain insecurity. However, according to the perspectives of Raman and Shahrur [
1], Acemoglu et al. [
2], and Kolay et al. [
3], a higher supply chain concentration increases the risk faced by firms if major trading partners, whether suppliers or customers, encounter problems. Thus, the supply chain concentration may have a significant impact on a firm’s supply chain security. Supply chain concentration refers to the proportion of transactions with a firm’s top trading partners relative to all its transactions; the higher this proportion, the greater the supply chain concentration [
4]. Simultaneously, the quality of export products is also an important area of research. Enhancing export product quality contributes to environmental protection by reducing waste emissions and other related aspects, thereby promoting environmental sustainability [
5]. Therefore, the impact of the supply chain concentration on export product quality represents a valuable research question. The following sections will analyze this impact in detail.
Although research on the supply chain concentration has been ongoing for a long time, recent years have witnessed an amplified scholarly focus on this topic, possibly driven by the impact of the COVID-19 pandemic. However, the conclusions of existing literature regarding the effects of the supply chain concentration are not entirely consistent. Some studies argue that the supply chain concentration can be beneficial for firms, while others suggest that it may have negative effects.
Given that technological capability and financial resources are critical factors for firms in producing high-quality products, the literature on how the supply chain concentration impacts these aspects is closely related to this study.
Regarding technological capability, there are differing perspectives in the current literature. Some studies investigate scenarios in which suppliers and customers may influence each other, while others focus on scenarios where such mutual influence does not occur. In situations where suppliers and customers do influence each other, Peters [
6] took a novel approach by examining the impact of customer concentration on R&D investment, while also focusing on the concentration level of suppliers. Using data from the German automotive industry, the study found that when the supplier market is less concentrated, a firm’s R&D investment decreases as the customer market concentration increases. Subsequently, analyzing the impact of the supply chain concentration from a theoretical perspective could provide a more systematic approach to the issue, as suggested by Krolikowski and Yuan [
7]. Their study, conducted within the framework of incomplete contract theory, resource dependence theory, and transaction cost economics, also emphasized the issue of switching costs. It found that an increase in the customer supply chain concentration may promote supplier innovation; however, when customers possess strong bargaining power, it may inhibit supplier innovation. In scenarios where suppliers and customers do not influence each other, Zhu et al. [
8], focusing on inventory management, concluded that an increase in both supplier and customer concentrations can benefit a firm’s productivity. The study also made a notable contribution by identifying the substitutive role of digitalization in mitigating the effects of the supply chain concentration. Jiang et al. [
9] found that the supplier concentration negatively affects firm innovation, while the customer concentration has a positive impact. Furthermore, when emphasizing ownership differences, they discovered that the supply chain concentration had a greater impact on the innovation of private firms. Liu et al. [
10] focused on comparing the impacts on different types of innovation and found that the customer concentration may lead firms to prioritize incremental innovation over breakthrough innovation.
Regarding financial resources, the current literature also presents mixed views on the impact of the supply chain concentration on a firm’s ability to secure funding. Some studies analyzed this impact within the scenarios of overall financing conditions, while others investigated its effects specifically within the scenarios of bank loans. In the research on overall financing, Upson and Wei [
4] emphasized the issue of information asymmetry and innovatively analyzed the income differences for investors facing increased information asymmetry. Their study found that an increase in the supply chain concentration may be more beneficial for firm financing. When firms engage in diversified procurement, partnering with multiple suppliers, their equity and debt costs may rise, and they may face more severe information asymmetry issues. Additionally, firms are more negatively affected when suppliers are in poorer financial condition. However, Fang et al. [
11], using data from small and medium-sized firms, found that an increase in the supplier concentration negatively impacts credit ratings, while an increase in customer concentration positively affects credit ratings. Moreover, as different financing channels may be impacted differently, a more detailed analysis is important. Since bank loans are often the most common financing channel, they represent a particularly significant area of research. In banking loan research, Campello and Gao [
12] made a noteworthy contribution by examining both pricing and non-pricing aspects in loan contracts. They found that a higher customer concentration leads to higher loan interest rates, more loan restrictions, and shorter loan terms. Furthermore, increased customer concentration also affects the duration and intimacy of a firm’s relationship with banks, which may hinder firm financing. Shi et al. [
13] conducted a noteworthy analysis based on signaling theory and found that the customer concentration has a favorable impact on bank loans, while the supplier concentration has an unfavorable impact. Ma and Gao [
14], focusing on the role of supply chain relationships in sustainable development, innovatively examined the impact of the supply chain concentration on the scale, cost, and duration of loans from different loan characteristics. Their study discovered that an increased supply chain concentration has a positive impact on all three aspects. Furthermore, when there is less uncertainty among supply chain partners, the positive effects of the supply chain concentration on loan size, cost, and term are even greater. However, the study suggested that a more systematic analysis of supply chain operations is needed, utilizing more sophisticated theoretical models.
In the literature on export product quality, existing research primarily focuses on measuring export product quality and identifying its influencing factors.
Regarding the measurement of export product quality, representative studies include those of Khandelwal et al. [
15] and Shi and Shao [
16]. Khandelwal et al. [
15] constructed an empirical model based on the prices and quantities of exported products to measure export product quality, controlling for important product fixed effects and destination–year fixed effects. In this study, export product quality was measured as the ratio of residuals from the regression to the difference between elasticity and one. In contrast, Shi and Shao [
16] measured export product quality by utilizing product trade demand and standardized the quality metrics to facilitate better comparisons. This methodology is widely used in research on China’s export product quality. Both papers share similarities, likely because they adhere to relevant export trade theories.
In addition to measuring export product quality, which is crucial for its improvement, the factors affecting export product quality have received considerable attention. Regarding the factors influencing export product quality, the existing literature can be divided into two categories: macro and micro. At the macrolevel, macroeconomic factors have a broader impact on export product quality, leading many studies to address this issue. Furthermore, due to the direct impact of internationalization factors on export product quality, some literature has examined the influence of internationalization-related factors. Additionally, as some studies argued that the government is a major player in shaping the macroenvironment, the literature has also explored government-related factors.
In the literature on internationalization-related factors, some studies examined scenarios that focus on tangible factors, while others explored scenarios that emphasize intangible factors. Regarding tangible factors, Anwar and Sun [
17] made a marginal contribution by employing a firm heterogeneity theoretical model. Their study found that a higher presence of foreign firms within an industry positively affects export quality. Zhang et al. [
18] took a relatively unique perspective by examining the impact of internationalization on export quality from the standpoint of foreign-invested banks. They found that foreign-invested banks have a beneficial effect on export quality. Additionally, this study emphasized the distinction between different types of trade, concluding that the positive impact of foreign investment is more pronounced in general trade enterprises. In terms of intangible factors, Xiong et al. [
19] made a marginal contribution by examining the impact of foreign divestment. Their analysis revealed that foreign divestment has a significantly negative effect on export quality. Hayakawa et al. [
20] focused on the differences in foreign direct investment (FDI) within the service sector, finding that FDI in the service industry promotes improvements in export product quality. However, this effect is more pronounced for foreign-invested enterprises. Oladi and Beladi [
21] innovatively studied the “spillover effect” of multinational corporations’ investments in underdeveloped regions on product quality. The research concluded that under conditions of price competition, the “spillover effect” of multinational corporations’ investments in product quality in underdeveloped regions may benefit the improvement of export quality in these areas. Additionally, Yan et al. [
22] emphasized the differences in firm productivity and found that outward foreign direct investment (OFDI) positively affects export product quality, with a more significant impact on low-efficiency firms. However, Lu et al. [
23] uniquely discovered that an increase in FDI may have a negative impact on export quality. Consequently, among the literature on tangible and intangible factors related to internationalization, it is more often believed that internationalization has a beneficial impact on improving export product quality. Regarding the government-related factors, some studies focused on scenarios examining government revenue and expenditure, while others focused on scenarios where the increasingly serious issue of environmental degradation is a key concern. Regarding government revenues and expenditures, Leng et al. [
24] made a marginal contribution by employing dynamic analysis to conclude that fiscal pressure on the government may positively impact export product quality. However, Wu et al. [
25] took a novel approach by examining the issue from the perspective of debt acquisition, discovering that an increase in government debt negatively impacts export quality. As environmental degradation has become more severe, environmental protection has garnered greater attention. Given that effective environmental protection largely depends on government regulations, many studies have investigated the impact of these regulations on export product quality. In terms of the impact of environmental regulations, Xiong and Zhu [
26] argued that such regulations could potentially improve export product quality. Moreover, the study emphasized the differences between upstream and downstream cities, concluding that the effect of environmental protection on export product quality is stronger for downstream firms. However, He and Tang [
27] marginally contributed by analyzing the local governments’ responses to central policies, finding that local environmental policies could negatively impact export product quality. In summary, both government revenues and expenditures, as well as environmental protection, can have either positive or negative effects on export product quality.
At the microlevel, since micro-factors tend to have a more focused impact on export product quality, many studies have been conducted in this area. Since technological capability and capital are important for firms to produce high-quality export products, the literature surrounding these factors is likely to be more pertinent to this study.
Regarding technological capability, given the direct relationship between a firm’s technological level and export product quality, this area has garnered significant scholarly attention. Among the current research frontiers, digitalization and robotic intelligence stand out.
In terms of digitalization, some studies focused on scenarios where the relationship between digitalization and export quality is linear, while others examined scenarios where this relationship is nonlinear. In the context of linear relationships, Chiappini and Gaglio [
28] made a marginal contribution by employing an extended gravity model, finding that digitalization positively impacts export quality. Wang and Ye [
29] also found that digitalization enhances export quality. However, the study innovatively revealed a negative effect of digitalization, specifically in widening the wage gap within firms. Nonetheless, it primarily focused on firm-level export quality, leaving product-level export quality for further investigation. Moreover, due to data availability constraints, the study only used data from 2007 to 2015. Zhang and Duan [
30] emphasized that under the context of market integration, digitalization can improve export quality; however, the negative moderating effect of market segmentation should be taken into account. Since excessive development in many areas can lead to negative outcomes, it is crucial to verify whether overdevelopment in digitalization, despite its advanced nature, might have adverse effects. Therefore, investigating the nonlinear impacts of digitalization could be valuable. In the context of nonlinear relationships, Zhang and Duan [
31] found that the effect of digitalization on export quality follows an inverted U-shape. Furthermore, this study placed significant emphasis on the importance of digital infrastructure. It found that insufficient support from infrastructure for digitalization may reduce the beneficial effects of digitalization on export quality, particularly on the left side of the “inverted U-shaped” curve. However, the discussion in this study on the common advantage of enhanced information availability through digitalization could be further elaborated. Wang et al. [
32], focusing on electromechanical products, also concluded that the relationship between digitalization and export quality is inverted U-shaped. However, the study reached this conclusion through theoretical analysis alone, indicating that further empirical testing is needed to validate the findings. In summary, in the context of linear relationships, the literature generally views digitalization as beneficial for improving export product quality. In contrast, in nonlinear relationships, the literature suggests that the impact of digitalization on export quality is inverted U-shaped.
In terms of robotics, some studies focused on scenarios where the relationship is linear, while others examined scenarios where the relationship is nonlinear. However, as research in this field has only recently begun to develop, the current body of literature may still be limited, but it is expected to grow in the future. In the context of linear relationships, DeStefano and Timmis [
33] studied the relationship between robotics and export product quality, finding that the use of robots improves export product quality, particularly for products that initially had lower quality. This effect is also more pronounced in developing economies, where export product quality tends to be lower. Furthermore, the authors of [
33] emphasized how variations in types of robotics affect export product quality across different countries and regions. However, due to data availability, the study only used country–industry-level data, lacking a more granular analysis of different institutions within industries. Lin et al. [
34] also found that the application of robotics has a positive impact on export product quality. Moreover, they highlighted that an extended import period enhances the beneficial effects of robotics on export quality. However, while robotics is considered an advanced technological tool, it raises an important question: could excessive use of robotics lead to adverse effects? Therefore, exploring the nonlinear impact of robotics application could be meaningful. In the context of nonlinear relationships, Lu et al. [
35] conducted an innovative analysis using an endogenous quality selection model and found that the effect of robotics on export product quality follows an inverted U-shape. The analysis also concluded that robotics impacts export product quality through channels such as improving productivity and suppressing innovation. In summary, the views on robotics application in both linear and nonlinear relationships are likely similar to those in the digitalization literature. In linear relationships, the literature generally suggested that robotics application is beneficial for improving export product quality. In nonlinear relationships, the literature indicated that the impact of robotics on export product quality is inverted U-shaped.
Moreover, since improved technological capabilities require investment to better produce high-quality products, financial resources are also a crucial factor in producing high-quality export products. Therefore, many studies have investigated the impact of firm financing on export product quality. Among these studies, some conducted their analysis within the scenarios of overall corporate financing and export product quality, while others focused on more specific scenarios, conducting their research within the scenarios of bank funding and export product quality. Regarding overall financing, Hu et al. [
36] found that financing constraints negatively affect export product quality. Moreover, this study, within the context of advancing market integration in China, emphasized the importance of improving the market system. It found that enhancements in the market system can mitigate the adverse effects of financing constraints on export product quality. Choi [
37] innovatively employed a heterogeneous firm model, incorporating credit constraints and quality selection. The study found that a reduction in financing costs benefits the improvement of a firm’s export product quality. Ma et al. [
38] found that green finance benefits the improvement of export product quality. Additionally, this study made a marginal contribution by examining the impact of green insurance, finding that green insurance positively influences the improvement of export product quality. Given that different financing methods can have varying impacts, and since bank loans may be the most common method for firms to obtain financing, many studies have explored the effects of bank loans on export product quality. In terms of bank financing, Sui et al. [
39] argued that bank loans positively affect export product quality. Furthermore, this study highlighted that state-owned enterprises may experience greater benefits from bank loans. From a reverse perspective, Qiu et al. [
40] examined bank loan restrictions and found that easing these restrictions can enhance export product quality. Additionally, the study also highlighted the differences in financing dependence among firms, finding that firms with higher levels of financing dependence experience more significant impacts from the relaxation of bank loan restrictions. Accordingly, the literature generally suggested that improvements in financing are beneficial for enhancing export product quality.
Based on the above, there may not yet be a unified conclusion regarding the impact of the supply chain concentration, and there is limited literature on how it affects the quality of exported products. Specifically, the impact of the supply chain concentration on technological capability, which is potentially the most critical factor for firms producing high-quality export products, remains inconclusive.
Consequently, this study aimed to investigate whether the supply chain concentration affects export product quality, thereby providing insights to enhance supply chain management practices and improve the quality of exported products. By analyzing data from Chinese A-share (A-shares refer to common stocks issued by companies within mainland China, which are subscribed to and traded in RMB by domestic institutions, organizations, or individuals) listed companies on the Shanghai and Shenzhen stock exchanges between 2001 and 2015, this research established that an increased supply chain concentration adversely affects export product quality, a conclusion supported by robustness checks. Furthermore, heterogeneity analysis revealed that the adverse effects of the supply chain concentration are less pronounced in technology-intensive firms, firms with banking relationships, firms with CEOs having overseas backgrounds, and firms with top executives possessing expertise in digital-related fields. Mechanism analysis indicated that the supply chain concentration may influence export product quality through mechanisms including firm size, production efficiency, and supply chain effectiveness. Lastly, moderation effect analysis suggested that regional fixed asset investment, overseas subsidiaries, and advanced industrial structures can positively moderate the negative impacts of the supply chain concentration on infrastructure resilience, firm structure resilience, and industry structure resilience.
This paper may offer the following marginal contributions: (1) Providing literature support. Given the limited research on the impact of the supply chain concentration on export product quality, this study aimed to fill that gap. Moreover, as the COVID-19 pandemic has underscored the critical importance of supply chain issues, pursuing high product quality is essential for the stable development of international trade and supports environmental protection. Therefore, studying the relationship between these two crucial aspects is of significant practical relevance. (2) Conducting targeted heterogeneity analysis. This includes examining two crucial factors that influence the production of high-quality export products—technological capability and financing—as well as two key aspects that affect the impact of supply chain concentration: the CEOs’ overseas background and the top executives’ expertise in digital-related fields. Since technology, capital, and management are closely linked to the subject of this study, relevant research may offer important practical insights for firms with differences in these areas to better manage the relationship between supply chain concentration and export product quality. Therefore, this analysis is likely to be of significant practical relevance. (3) Conducting a comprehensive analysis of impact pathways. This study examined the influence of supply chain concentration from the dual perspectives of size and efficiency, both of which are critical in firms’ operations. The analysis revealed that firm size, production efficiency, and supply chain efficiency are pathways through which the supply chain concentration impacts export product quality. Moreover, analyzing both scale and efficiency together may better improve export product quality. On one hand, increasing efficiency while expanding scale could lead to a more effective improvement in export product quality. On the other hand, increasing scale while improving efficiency might provide a stronger material foundation for enhancing product quality. Therefore, simultaneously analyzing both scale and efficiency could have significant practical implications for systematically mitigating the negative effects of the supply chain concentration on export products. (4) Analyzing the effects of resilience. This paper examined the role of resilience from the perspectives of infrastructure resilience, firm structure resilience, and industrial structure resilience. The findings suggested that stronger resilience in these areas can mitigate the negative impact of the supply chain concentration on export product quality. Therefore, the findings from this part of the study may hold significant practical relevance for understanding how to use external resilience to mitigate the negative impact of the supply chain concentration on export product quality.
The remainder of this paper is structured as follows:
Section 2 presents the theoretical analysis and hypotheses,
Section 3 explains the research design,
Section 4 discusses the empirical results,
Section 5 offers further discussion, and
Section 6 concludes with policy implications.