A meta-analysis of the effects of sponsorship disclosure in influencer marketing

To disclose or not? Despite valuable insights on the impact of influencer disclosure, marketers and influencers remain hesitant. This research quantitatively integrates 288 effect sizes from 37 studies involving 12,721 participants to draw generalized conclusions. Our findings reveal that influencer sponsorship disclosure increases persuasion knowledge and brand recall, but reduces credibility, while its overall effects on attitude and conative responses are insignificant. To address the heterogeneity in affective and conative consumer responses, and guide disclosure practices, we identify four moderator groups—disclosure characteristics, stimulus characteristics, consumer characteristics, and controls—and examine their moderating effects through a meta-regression model. Our findings suggest that sponsorship disclosure is more effective when disclosed by others (vs. the influencer), presented as a hashtag (vs. a statement), longer in length, appeared in video (vs. text or image) post, and shown to adults (vs. children and adolescents). This research is significant for influencers, marketers, and policymakers in promoting ethical and effective consumer communication.