Influencers in the not-too-old-not-too-young sweet spot make the most effective brand endorsers, according to a new study.
Across four different experiments testing how the age of influencers affects marketing outcomes, the researchers saw the same inverted U pattern in their results, with the youngest and oldest influencers underperforming those that sat somewhere in between.
According to one of the experiments, an average 18-year-old influencer on Instagram will get more engagement on their posts as they approach the optimal age of 27, equivalent to a 55% increase in followers. But then, engagement will decline as they head to 40, equivalent to losing 62% of their followers.
An experiment with AI-generated influencers on TikTok meanwhile, showed that influencers around the optimal age of between 47 and 55 generated 70-90% more views, compared with a 20-year-old persona.
Another experiment, again with AI-generated influencers, demonstrated that the same dynamics applied when they asked participants how likely they were to buy a product from influencers at different ages. In this experiment, the sweet spot was between 37 and 45 years old.
The researchers say that the study lends weight to the source credibility theory of influencer marketing effectiveness. This model states that as influencers age their perceived attractiveness declines but their perceived credibility increases. And these two factors have a multiplicative effect on each other, rather than an additive one. So, an influencer who is both averagely attractive and averagely credible will outperform one who is exceptionally attractive but has little credibility because 5 X 5 is greater than 10 X 1.
The weight that audiences give to either credibility or attractiveness depends on a lot of different factors, however. For example, in low trust media environments, audiences place a premium on credibility, and the optimal influencer age increases. The researchers suggest that this is why the optimal age in the Instagram study was considerably lower than those in the studies with AI-generated influencers — because AI-generated influencers put audiences on their guard.
The study, by Clara Galle, Vanessa Lau and Florian Dost, is called Beyond youth: The optimal age for influencer credibility and marketing success, and it has been published online by the Journal of the Academy of Marketing Science.
