Research about persuasive effects of social media influencers as online opinion leaders 1990-2020: a review

This paper examines the 167 scholarly journal articles published from 1990 to 2020 related to persuasive effects of online opinion leaders and social media influencers. The USA, China and Germany were the three most common settings those studies were conducted. Most research articles explained the influence mechanism of social media influencers based on prior celebrity endorsement research, focusing on credibility, trustworthiness, homophily and parasocial interaction. In this review, we examine what we learned from the research literature in eight topics about the persuasive effects of influencers: 1) typology of influencers and methods to identify influencers; 2) relationship between the influencers and followers; 3) characteristics of the followers of influencers; 4) scope of influence of the influencers, 5) mechanism of influence; 6) approaches/strategies of influencers to brand endorsement; 7) measurement of influence outcomes; and 8) ethics of social media influencer marketing. A research agenda is proposed on how to further develop social media influencer marketing research based on the technology affordance of each social media platform and important areas that have been under-explored.