At the 2019 ICA conference in Washington, Loes Janssen, Emmelyn Croes, and I presented the results of our study about the effect of product-endorser fit and influencer popularity on advertising effectiveness.

Companies are increasingly using social influencers to promote their products on Instagram, but little is known about the effectiveness of using these social influencers. The goal of this study was to investigate the extent to which influencer popularity and product-influencer fit affect how people like and are persuaded by the influencer. Furthermore, we examine credibility and identification as possible underlying processes in the relation between product-influencer fit, influencer popularity, and product and endorser evaluations. We tested our hypotheses in an experiment among Instagram users (N=435), using a 2 (product-influencer fit: good fit vs. poor fit) x 2 (number of followers: moderate vs. high) between-subjects design. Participants were presented with a mock-up Instagram page of a fitness influencer, with either 5037 or 537k followers, promoting either a protein shake (good fit) or ice cream (poor fit). Analyses showed that influencers were liked more when they endorsed a fitting product, mediated by trust, identification, and similarity perceptions, but only when the influencer had a high number of followers. People indicated to be more likely to buy the product when there was good as compared to poor fit, mediated by trust, expertise, and identification, but again only for influencers with a high number of followers. Our findings show that product-endorser fit and popularity are also important factors for influencer success. Moreover, traditional processes such as parasocial interaction and credibility seem to explain these effects.

We have a poster of the presentation available here. We also gave a similar presentation at the Etmaal van de Communicatiewetenschap Conference, which you can download as well.