With a growing array of platforms and channels competing for consumer attention, advertisers have been increasingly looking for ways to understand which ads and placements drive engagement and sales – not just engagement and sales that would have happened anyway but true incrementality.
At the same time, retail media has emerged as the fastest-growing segment in advertising, projected to reach $81 billion in the US by 2027. But as the space matures, a hard truth is setting in: Not all “results” are created equal. Many marketers are still leaning on last-touch attribution and inflated ROAS figures that don’t reflect true business impact.
It’s time to shift focus from what’s easy to what’s essential: We must embrace incrementality as the new gold standard for retail media measurement. Let’s look at how retailers can benefit from easily enabling incrementality measurement on their platforms and why brands should prioritize it as a top KPI.
From attribution to actual impact
Traditional media measurement has long relied on correlational attribution – counting exposures and actions without questioning whether the behavior would have happened regardless of the media touch point.
Incrementality, by contrast, focuses on causality: Did that ad cause the customer to make a purchase? Or were they going to buy it anyway?
Incrementality studies expose opportunity cost and reveal what wouldn’t have happened if you hadn’t invested in media.
In other words, incrementality focuses on isolating the causal effect of advertising—whether it changed behavior, drove new revenue or increased value per transaction. It’s about separating correlation from causation. And it’s quickly becoming table stakes for marketers who want to future-proof their retail media investments.
Why now?
We’ve all heard the common refrain of 2025: Today’s economic climate is forcing marketers to do more with less. There’s less patience for vanity metrics and more pressure to prove business outcomes. That’s where incrementality shines.
You want your media to change people’s behaviors. You want it to encourage them to buy when they otherwise wouldn’t, to visit your store or app more frequently, to try a new product or expand into a new product category.
What counts as incremental?
Incrementality isn’t just about acquiring new customers; it’s also about deepening the value of existing ones. Did your ad inspire a lapsed customer to reengage? Did it increase purchase frequency or average basket size?
Incremental lift can take many forms:
- A loyal shopper who adds a new category to their basket.
- An occasional customer who registers or enrolls in your loyalty program
- A person who normally visits your store once weekly, but now visits twice weekly
In an omnichannel environment, where 80% of retail transactions still happen in-store, those nuances matter more than ever.
Measuring it isn’t easy (but it’s worth it)
Historically, incrementality has required resource-intensive methods: holdout groups, geo-based testing, synthetic control models. These methods were costly and often out of reach for all but the biggest players.
But technology and data accessibility have evolved. With advancements in data, experimentation and machine learning, marketers now have more tools than ever to measure true lift without having to sacrifice scale or speed.
Retailers that prioritize incrementality can gain a competitive edge by proving the value of their retail media networks to brand partners.
The future of retail media is omnichannel
Due to the growing cost and diminishing returns of strictly online retail media through formats like on-site display ads or sponsored products, the next wave of growth in retail media is happening off-site: across the open web, as well as on screens in near- and in-store physical environments.
Brands that limit their measurement to online clicks or conversions are missing a massive part of the story. An online ad that prompts someone to visit a physical location and make a purchase might not show up as a digital sale. But it absolutely impacts the bottom line. The same goes for an ad that someone sees in-store that introduces them to a brand or product that they go on to research and ultimately buy. Being able to measure that kind of lift – especially when integrated with mobile location signals – makes incrementality a superpower.
What true incrementality support looks like
Meaningful advertising should lead to measurable outcomes. That’s why effective measurement frameworks should prioritize incrementality at every stage.
For example:
- First-party behavioral data: T-Mobile Advertising Solutions analyzes app usage and privacy-centric store visitation data across our mobile network to detect real-world changes in consumer behavior.
- Geo-based lift testing: Particularly useful for in-store and digital out-of-home campaigns, we use DMA-, ZIP-, and store-level control and treatment groups to isolate true impact.
The creation of a holdout group is also a key part of measuring incrementality. A holdout group is a group of people or stores or geographies that are not exposed to media. The group should be representative (in composition and behavior) of the treatment group receiving media exposures. This enables marketers to isolate the impact of their media and provides a baseline for what consumer behavior would look like if no campaign were run.
Incrementality might not be the simplest metric to calculate. But it’s the most honest one. It forces marketers to ask tough questions about what’s really working. And in doing so, it helps uncover untapped opportunities for strengthening campaigns.
Retail media is entering a new era that will span aisles as much as ad servers. To keep up, marketers and retailers alike need to adopt more rigorous, outcome-driven standards.
The industry needs to stop rewarding what’s easy to measure and start investing in what matters most: advertising that actually changes behavior.
