Loïc Sfiligoï, Co-founder and CSO at Pubstack, addresses a paradox that the whole industry faces – more volume, less value, in a growing market. So what can be done?

Here's a paradox that should concern everyone in this industry. The UK digital advertising market grew 13% in 2024. Advertiser budgets were there. And yet, programmatic display eCPMs fell by 10.5% over the same period, while impression volumes grew by 10.5% (Pubstack, State of Programmatic UK 2025). More volume. Less value. In a growing market.

This is not a cyclical anomaly. It is a structural one — and understanding it matters for the future of the open web.

Where did the value go?

Over the past decade, the buy side built an increasingly sophisticated decisioning stack: DSPs, DMPs, verification layers, attention metrics, brand safety tools. Each layer captures a slice of the media budget before a single penny reaches the publisher. According to the Association of National Advertisers, publishers take home just 30 to 40 cents of every advertiser dollar spent. The ISBA/PwC Programmatic Supply Chain Transparency Study found that 35% of advertiser spend simply never reaches the publisher.

The money didn't disappear. It migrated: from the impression, toward the technology that decides where to buy it.

The most direct proof of this shift is the CPM gap between direct and programmatic. Direct deals consistently generate 3 to 5x higher CPMs than open programmatic for the same inventory. The difference isn't the audience or the content. It's who controls the decision to buy.

The market can't see quality

What makes this particularly damaging is that programmatic has made quality invisible. In open auction, the CPM gap between a premium publisher and a made-for-advertising site is £0.01 — £0.75 versus £0.74 (Pubstack data). One penny, separating two environments at opposite ends of the quality spectrum.

A publisher can multiply their ad load by 30 and see unit CPMs fall by just 31%: from £0.84 to £0.58. The market barely penalises clutter. And if it doesn't punish bad actors, it certainly doesn't reward good ones.

This invisibility has consequences for advertisers too. Paying virtually the same rate for a clean page on a quality title and a banner-heavy click farm is not a publisher problem, it's an ecosystem problem. It explains why luxury brands have largely abandoned open web programmatic, not for lack of interest in the audiences, but because the signals they value most — editorial context, page exclusivity, controlled placement — simply don't travel through the chain.

Publishers hold the answer

Here is what makes this situation genuinely absurd: publishers already hold the data the buy side is spending significant resources to reconstruct. Real-time viewability. Actual clutter levels. Deterministic engagement signals. The buy side approximates all of this through crawling, campaign benchmarks, and third-party tools. Publishers have the ground truth. They're just not surfacing it.

The emergence of curation confirms there is demand for sell-side signals: curated inventory commands CPMs 25% higher than open market rates on average (ANA, 2024). But curation as it stands uses weak signals, operates on a fraction of inventory, and sends the margin to intermediaries, not to publishers.

The path forward isn't more bidders. Publishers in the UK have already increased their bidder count by 20% on desktop year-on-year: eCPMs kept falling. The path forward is decisioning: the ability to package inventory by real outcomes — viewability, attention, exclusivity — based on signals only the publisher holds, made readable to buying algorithms.

The open web hasn't lost its value. It has lost its ability to demonstrate it. That's the problem worth solving.