The advertising industry has always had a weakness for the new thing, and an even greater weakness for spending heavily on the new thing before anyone has figured out how to prove it works. Influencer marketing, which has graduated from curiosity to line item to, in some cases, the dominant allocation in a media plan, appears to have reached the stage where it must now justify itself to people who were not in the room when the decision was made.

According to a report in Marketing Week, the Institute of Practitioners in Advertising has released what the publication describes as "among the first credible and independent studies" to suggest that influencer-led campaigns often outperform traditional media. That the study is notable partly for its mere existence tells you something about where the category stands. (The advertising business has had decades to refine its measurement of television effectiveness; influencer marketing is working with a somewhat shorter runway.)

The publication surveyed marketers on how they determine the impact of their influencer spending and found a profession still feeling its way. Some are incorporating creator activity into econometric models. Others, the report noted with admirable directness, are "not being made on vibes" but acknowledge "there is still work to be done."

Social media more broadly appears to have won the confidence of its buyers, at least by their own account: 77.7 percent of marketers surveyed said measuring its impact was easy or very easy. Whether those measurements would satisfy a chief financial officer is a separate question, and one the report politely declines to answer.

In a related item, Nestlé's KitKat brand earned attention for turning the theft of 12 tonnes of its chocolate bars in Italy into a social campaign. The effort succeeded, according to global head of marketing strategy Maureen Kingston, because the brand had spent 70 years building the equity that allowed it to move quickly. "You don't need 70 years," Marketing Week observed, "but you do need the foundations."

It is a lesson that applies equally well to measurement. The spending is already here. The proof is still under construction.

Original story published in Marketing Week: "Influencer effectiveness and KitKat's social success: Your Marketing Week"