What the Research Actually Says About Influencer Marketing

Most influencer marketing advice is anecdote and instinct. But marketing academia has been building empirical evidence on this for nearly a decade — one 2025 meta-analysis alone pooled 1,531 effect sizes from 251 papers (Pan, Blut, Ghiassaleh & Lee, 2025, Journal of the Academy of Marketing Science). This piece distills the findings you can act on this quarter. Every claim is sourced, so you can lift it straight into an internal deck.

1. More followers is better — with two important exceptions

De Veirman, Cauberghe & Hudders (2017, International Journal of Advertising) tested how an Instagram influencer's follower count shapes brand attitude. The baseline result matches intuition: influencers with more followers are perceived as more likeable, and that likeability runs through a perception of popularity.

The exceptions are where it gets useful.

• If the influencer follows very few accounts themselves, a high follower count can actually reduce likeability
• For divergent, distinctive products, a high-follower influencer lowered the brand's perceived uniqueness — and with it, brand attitude

That second one matters if you sell something niche. Casting a mega-influencer can make a distinctive brand read as the thing everyone already uses. Big reach is not automatically the safe choice.

2. Do not hide the sponsorship

Leung, Gu, Li, Zhang & Palmatier (2022, Journal of Marketing) analysed influencer marketing through an engagement-elasticity lens — effectiveness relative to cost. Three factors raised effectiveness: influencer originality, follower size, and sponsor salience, meaning how clearly the sponsoring brand shows up in the post.

Many brands still ask creators to blend the product in so it does not feel like an ad. The evidence points the other way: posts where the brand was clearly present performed better. The instinct to bury the sponsorship is not supported.

One distinction worth keeping straight: sponsor salience is about making the brand visible inside the content, while #ad and #sponsored labels are a legal disclosure requirement (FTC in the US, and equivalent rules elsewhere). Different concepts — but the practical conclusion points the same way. Obscuring a paid relationship carries legal risk and buys you nothing in performance.

3. Three places where moderate beats maximum

The most actionable finding in Leung et al. (2022) is that three variables follow an inverted U-shape. More is not better, less is not better — the middle wins.

• Influencer activity: posting too rarely and posting too often both reduce effectiveness
• Follower-brand fit: an audience that matches the brand too perfectly performs worse
• Post positivity: relentlessly positive tone backfires

The second is genuinely counterintuitive. We normally treat perfect audience overlap as the ideal. But too much overlap may add no incremental reach, and it can read to followers as an obvious ad. The third is the same lesson in a different form: a review with no drawbacks does not earn trust. Honest balance outperforms flawless praise — and now you have data for that argument.

The same study also found that posts announcing new product launches reduced effectiveness. Launch announcements are a job for brand-owned channels; creators are better used to show how an existing product actually fits into a life.

4. Expertise works differently depending on your goal

Hughes, Swaminathan & Brooks (2019, Journal of Marketing) studied sponsored blogging campaigns and found that the value of influencer expertise depends on campaign intent and platform. High expertise was more effective when the goal was raising awareness; the pattern differed when the goal was driving trial. And the same expertise failed to drive engagement once the post moved to a different platform.

Translation for practitioners: decide the objective before you shortlist anyone. For awareness, authority in the category wins. For conversion, familiarity and similarity may beat credentials. There is no good influencer in the abstract — only the right one for this objective.

5. Influencers beat brand-owned ads, and match celebrities

Lee, Walter, Hayes & Golan (2024, Social Media + Society) meta-analysed 39 experiments covering 13,766 participants. Social media influencers outperformed brand-owned advertising. Compared with celebrity endorsers, no significant difference emerged.

That is a budget argument. If the effect is comparable, the option that costs a fraction and lets you run several creators in parallel is the better allocation.

The five judgement calls this changes

• Think twice before putting a mega-influencer on a niche, distinctive product
• Keep the brand visible. Disclosure is required, and it does not cost you performance
• Do not shortlist only perfect-fit audiences — moderate fit is optimal
• Allow honest tone instead of wall-to-wall praise
• Set the objective (awareness vs conversion) before choosing the creator type

Part of this is built into imktr's workflow. Campaign KPIs are set in the setup wizard before anyone is shortlisted, briefs capture selling points as keywords while leaving tone and voice to the creator, and the upload stage checks ad disclosure. If you would rather run campaigns on verified criteria than instinct, the workflow already follows this shape.

References

• De Veirman, M., Cauberghe, V., & Hudders, L. (2017). Marketing through Instagram influencers: the impact of number of followers and product divergence on brand attitude. International Journal of Advertising, 36(5), 798–828.
• Hughes, C., Swaminathan, V., & Brooks, G. (2019). Driving Brand Engagement Through Online Social Influencers: An Empirical Investigation of Sponsored Blogging Campaigns. Journal of Marketing, 83(5), 78–96.
• Leung, F. F., Gu, F. F., Li, Y., Zhang, J. Z., & Palmatier, R. W. (2022). Influencer Marketing Effectiveness. Journal of Marketing, 86(6), 93–115.
• Pan, M., Blut, M., Ghiassaleh, A., & Lee, Z. W. Y. (2025). Influencer marketing effectiveness: A meta-analytic review. Journal of the Academy of Marketing Science, 53, 52–78.
• Lee, J., Walter, N., Hayes, J. L., & Golan, G. J. (2024). Do Influencers Influence? A Meta-Analytic Comparison of Celebrities and Social Media Influencers Effects. Social Media + Society.