Every major advertising channel in history has eventually had to answer the same question: can you prove it works? Television answered it, imperfectly, with Nielsen ratings and brand lift studies. Digital display advertising answered it with click-through rates. Search advertising answered it with last-click attribution tied directly to purchases. Each answer was flawed, but there was an answer.

Influencer marketing, the fastest-growing ad channel of 2026, still does not have a good one.

US influencer and creator economy ad spend is on track to hit $43.9 billion this year, according to industry estimates — up sharply from the year before. CMOs are pulling budgets from television and even from some digital performance channels to fund creator partnerships. Yet according to research published this year, 57% of marketers who run influencer campaigns still say they cannot accurately measure the ROI. They are scaling something they fundamentally cannot track.

That is not a minor operational problem. It is a structural flaw at the heart of the fastest-growing line item in most marketing budgets.

Why measuring influencer ROI is so hard

The straightforward explanation is that influencers operate at the top and middle of the funnel, not the bottom. When someone sees a creator talking about a skincare brand in an Instagram Reel, they do not usually click a link and buy immediately. They might search for the brand three days later. They might see a display ad retargeting them on a different site. They might walk into a store and pick it off the shelf. When the purchase eventually happens, last-click attribution models give the credit to Google or the retargeting pixel — not the influencer who planted the idea.

Apple’s iOS privacy changes made this worse. Before 2021, brands could track user behaviour across apps and websites with reasonable accuracy. After iOS 14.5, cross-app tracking requires explicit user consent, and most users do not give it. The data trail that connected an influencer post to a downstream purchase got significantly shorter.

The result is that most influencer measurement today relies on things that are easy to track but do not actually tell you whether the campaign worked: follower counts, likes, comments, reach, and impressions. These numbers look good in a deck. They do not tell you whether a single person bought the product.

The $5.78 figure that is probably misleading you

The industry benchmark that gets cited most often is that influencer marketing returns $5.78 for every $1 spent on average, with top campaigns reportedly returning $18 to $20. This number appears in almost every “why you should invest in influencer marketing” presentation.

It deserves some scepticism.

These figures are typically calculated by brands that set up proper tracking in advance — unique discount codes, dedicated landing pages with UTM parameters, affiliate links that pay on conversion. These are also the brands that are most sophisticated about influencer marketing generally. They represent a minority of campaigns. The majority of influencer deals are still struck on the basis of a flat fee, a free product, or a gifting arrangement, with no tracking infrastructure whatsoever. The ROI from those campaigns is simply unknown, so it does not appear in the average.

This creates survivorship bias in the data. The campaigns that can be measured look good. The campaigns that cannot be measured are invisible. The overall picture therefore looks much rosier than the full reality probably warrants, as we touched on in our piece on brands getting obsessed with ROAS metrics at the expense of brand building.

What the smart brands are doing differently

The brands that are successfully measuring influencer ROI are doing it by changing how they structure the partnerships from the beginning, not by applying better analytics after the fact.

A few specific approaches are making a real difference.

Performance-based pay structures. Instead of paying a flat fee for a post, some brands are moving to arrangements where creators earn a base rate plus a commission on sales generated through their specific affiliate link. This aligns the creator’s incentive with the brand’s actual goal and builds attribution into the structure of the deal itself. The downside is that many established creators refuse these arrangements — they do not want their income to depend on conversion rates they cannot control.

Pre- and post-campaign brand lift studies. These measure shifts in brand awareness, consideration, and purchase intent among exposed versus unexposed audiences. They do not tell you about direct sales, but they do tell you whether the campaign moved the needle on the metrics that drive sales over time. This is expensive, but it is the only rigorous way to measure top-of-funnel impact.

Geo-based incrementality testing. A few larger brands are running campaigns in specific regions and keeping matched regions dark as control groups, then comparing sales data between regions. This is genuinely hard to execute cleanly, but it produces actual proof of sales lift rather than correlation.

The common thread in all these approaches is that they require planning before the campaign launches, not measurement after. As we covered in our analysis of first-party data strategies for 2026, brands that invest in data infrastructure before they need it are consistently outperforming those that try to retrofit measurement onto existing campaigns.

What you should do with your influencer budget right now

If you are spending significant money on influencer marketing and you do not have tracking infrastructure in place, the first thing to do is pause new deals until you do. This is a harder conversation than it sounds — creators want simple arrangements, managers push back on technical requirements, and some of your colleagues will argue that adding friction to the deal means you will lose good creators to competitors. That is probably true for some creators. It is also true that spending money on campaigns you cannot measure is a choice, not a necessity.

For campaigns already in flight, the most actionable thing you can do is segment your audiences immediately. Pull a list of customers acquired in the last 90 days and tag every one who used a promo code or clicked through a creator-specific link. Compare their lifetime value against your average customer baseline. If influencer-acquired customers buy more often and spend more over time — which some research suggests they do — that is the case you bring to your CFO to justify the spend.

The friction you need to prepare for: When you introduce performance-based pay or mandatory tracking links into creator negotiations, expect deal timelines to roughly double. Creators’ management teams are not set up for commission structures. Your legal team will need to review affiliate agreements. Your web team will need to build custom landing pages. The technical overhead of doing influencer marketing properly is significant and none of it shows up in the case studies that make the channel look effortless.

Influencer marketing probably does work for most brands. The honest answer is that most brands do not yet have the infrastructure to know for sure. That gap is worth closing before you scale the budget further.