*3.3. Helpfulness*

The helpfulness of online reviews has been a hot topic in social e-commerce [55] and marketing research over the past decade [56]. The research is mainly concerned with the prediction of review helpfulness [57], the determinants of review helpfulness [58], and the measurement of review helpfulness [59]. For example, Huang et al. examined the effect of message length together with aspects of review patterns and reviewer characteristics on review helpfulness [60]. Qazi et al. explained why some reviews are more helpful compared to others [61].

We found in the literature that the helpfulness of online reviews is closely related to the quality of it. Meanwhile, the quality of reviews has been regarded as important in constructing a reputation in a community, which in turn may lead the user to be considered as an opinion leader [62]. Some characteristics of the shared content, such as the attractiveness, quality, and composition of the images, are crucial for users to make the decision to follow a specific profile [63]. Other aspects related to quality, such as the comprehensiveness of the content [12], assertiveness, and emotion [64], have also been shown to be drivers of opinion leadership.

Bearing all these in mind, it is proposed that the helpfulness of the content contributed by social media influencers will influence the perception of opinion leadership. We propose hypothesis H3.

**Hypothesis 3 (H3).** *The more helpful content a member contributes, the more other members will establish a relationship with him/her and the more likely he/she is to become an opinion leader.*

## *3.4. Preferential Attachment*

Preferential attachment describes a social network in which network nodes with more relationships are more attractive to other nodes, similar to "the stronger the stronger, the weaker the weaker" concept. This phenomenon has been confirmed in many different networks such as scholar collaboration networks, Internet sites, etc. [65]. The main reason for this phenomenon is that network nodes search for star nodes in the network when establishing relationships and the value of establishing relationships with such star nodes is higher than the value of establishing relationships with ordinary nodes for judging star nodes [66]. In combination with the formation of opinion leaders, this phenomenon of preferential attachment seems to be more prevalent [67]. Therefore, we propose hypothesis H4.

**Hypothesis 4 (H4).** *The more followers a member has, the more other members will establish a relationship with him/her and the more likely he/she is to become an opinion leader.*
