For generations marketers have lived with John Wanamaker’s adage that half of advertising spend is wasted, we just don’t know which half.
The line has endured because measurement has always been imperfect. Even in the digital era, where precision promised to replace guesswork, blind spots remain. In 2026, one of the most expensive of these is digital media’s survivorship bias.
By optimising primarily against visible online conversions, brands risk overlooking the influence advertising has in store aisles, at restaurant counters and across other offline moments. That narrow view can distort performance, misdirect investment and quietly undermine annual planning.
Where attribution works today
Online-to-online journeys are well mapped: a shopper sees an ad, clicks through and completes a purchase on a website. Loyalty schemes add another layer of visibility by linking store sign-ups with later online behaviour.
These examples reflect genuine progress, but they represent the simplest journeys. In practice, most paths to purchase are neither linear nor fully digital. According to the ONS, as of 2025 29% of UK retail sales now occur online, which means the vast majority are still happening in-store.
For brands across many CPG, technology and hospitality categories, this creates a material gap. Digital activity may be driving footfall and revenue, but without evidence, budget naturally shifts elsewhere.
The in-store blind spot
In-store purchases often remain disconnected from digital media exposure. Even organisations with established loyalty programmes can struggle to connect offsite or onsite impressions with what happens at the till.
High-consideration categories highlight the issue. A TV purchase, for example, may unfold over several weeks, shaped by CTV, search, social and retail media listings. When the transaction happens in store, those digital signals can vanish from reporting, making campaigns appear less effective than they truly were.
The result is not just incomplete attribution, but flawed conclusions about which channels, audiences and messages are working.
Read more about how Currys connected cross-channel digital impressions to in-store sales
Common signs this blind spot is shaping decisions include
Shedding more light on outcomes
Addressing survivorship bias starts with broadening what counts as success. Online checkouts dominate reporting largely because they are easy to measure, not because they tell the full story. Bringing physical sales into KPIs helps rebalance the picture and prevents performance from being reduced to e-commerce alone.
Segments that look weak online may be completing their journeys offline. Older shoppers are a clear example: harder to observe digitally, yet often loyal and highly valuable in store. When these groups are consistently undervalued, investment drifts away from customers who matter most.
The most important step is connecting online exposure with offline outcomes. Loyalty programmes play a role by providing consented, individual-level purchase data that can be linked back to campaign exposure. But loyalty data often stops at a single retailer’s boundary.
When loyalty signals and data collaboration work together, the result is a more people-centred view of the journey. What matters is not the channel but recognising the same person across the moments that shaped their decision.
Media exposures that happen days or weeks before a sale are no longer invisible, and optimisation systems stop rewarding only the most obvious touchpoints.
Find out more about Epsilon Loyalty
A turning point
After decades of uncertainty, one of advertising’s longest-standing blind spots is beginning to close. Survivorship bias has skewed decisions by limiting marketers to what they could easily observe. With better data collaboration and a renewed focus on people rather than proxies, that limitation is no longer inevitable.
Key takeaways for 2026
Unlocking the in-store view is more than a technical improvement. It signals a shift away from chasing the easiest metrics and towards understanding real behaviour and real outcomes. By acknowledging survivorship bias and addressing it directly, marketers establish a clearer view of what works and greater confidence in where to invest for growth.
