EXPRESS: Endorsement Rate in Influencer Marketing

Influencer marketing has emerged as a prevalent marketing strategy for firms seeking to engage target customers, with significant research identifying various criteria for influencer selection. However, the role of endorsement rate—the proportion of an influencer’s brand-sponsored posts relative to their total social media posts—remains underexplored. This study addresses this gap by investigating how influencers’ endorsement rates affect the effectiveness of their subsequent sponsored posts. Using a multimethod approach, including two field studies and two controlled experiments across diverse platform contexts (e.g., Instagram, Twitter, Douyin), the findings reveal a consistent U-shaped relationship between endorsement rate and consumer engagement with sponsored posts. This pattern arises from the interplay of two countervailing forces: a higher endorsement rate enhances the influencer’s perceived brand recognition, yet it simultaneously raises audience suspicion of manipulative intent. Notably, organic product mentions and consistent brand endorsements can attenuate the impact of endorsement rates on consumer engagement. Beyond advancing research in influencer marketing and brand endorsements, these findings offer marketers a valuable framework for evaluating influencers and making more informed selections.