The $200 Billion Blind Spot: Why Social and Marketplaces Deserve More Credit

The problem isn’t that marketers lack data. It’s that the data often points in the wrong direction.

Speaking on stage at eTail Boston, Dom Devlin, Chief Product Officer at Fospha, made the case for tackling one of the most expensive oversights in retail marketing today: the chronic undervaluation of social and marketplace-driven demand.

The number he put on it: $200 billion. That’s the estimated value of sales influenced by discovery channels like TikTok, Meta, and Snap, but never credited, because the purchase took place on a marketplace rather than a brand’s own site.

Over the past decade, brands have diversified far beyond their own dot-com storefronts. Amazon now accounts for 40% of US eCommerce sales. TikTok Shop has doubled its footprint year-on-year. Walmart, Target, and Sephora have built marketplaces that are destination points for shoppers.

But measurement hasn’t kept pace.

With privacy rules limiting tracking pixels on platforms like Amazon and TikTok Shop, most marketers still measure in silos. Last-click and multi-touch attribution models, when used alone, can only see the transactions that happen on a brand’s own site.

The result? Channels that generate demand but don’t close the sale, like TikTok or Snap, are systematically undervalued. Fospha’s data suggests paid social ROAS can be undercounted by up to 40% when marketplace sales aren’t factored in.

And this isn’t just a rounding error. It’s a structural bias that shifts investment away from discovery and towards the channels that close, but may not create, demand.

For years, the industry tolerated some measurement fuzziness. Budgets were bigger, growth was easier, and privacy rules hadn’t yet dismantled cross-site tracking. That era is over.

With ad costs climbing, consumer acquisition slowing, and investors demanding profitability, marketers are scrutinising every dollar. Awareness and consideration campaigns are often the first to be cut.

Devlin warned that this reflexive cost-cutting can lead to what Fospha calls the bottom-of-funnel trap: higher acquisition costs, slower growth, and a shrinking pipeline of future customers.

“You can’t calculate a profitable ROAS if you’re only accounting for 43% of your revenue,” he told the audience, referencing a client example where nearly 60% of sales were happening off-site.

When marketplace sales aren’t captured in the same measurement framework as D2C sales, the numbers don’t just look incomplete, they distort the truth.

Consider a TikTok campaign that sparks discovery for a beauty brand. If a shopper sees an ad, searches the brand name, and buys on Amazon, last-click attribution credits the sale to Amazon and the TikTok spend looks like a loss.

Multiply that across thousands of transactions and entire channels can appear unprofitable, leading teams to pull budget from the very campaigns fuelling their future sales.

Fospha’s aggregated data suggests this misattribution is widespread. In beauty and personal care, TikTok Shop ads can drive a 20% halo effect on Amazon sales. In home goods and apparel, the halo can be even larger.

To tackle this, Fospha developed its Halo methodology, part of its unified, privacy-safe, full-funnel measurement approach, to quantify the indirect impact of channels across marketplaces.

For skincare brand Necessaire, the challenge was understanding how D2C marketing contributed to Amazon sales ahead of Prime Day. By integrating marketplace revenue into their unified ROAS, the brand could justify sustained investment in TikTok and Meta in the lead-up, rather than shifting budget entirely into bottom-of-funnel tactics. The outcome: 47% higher revenue than similar brands in Fospha’s benchmark cohort.

For Give Me Cosmetics, TikTok Shop was already a strong performer on paper. But once the halo effect on Amazon was included, the channel’s ROAS jumped 29%. This wasn’t just a “nice to know” stat, it prompted the team to increase daily spend by 73% while becoming more efficient overall.

These examples highlight the bigger point: without a unified measurement approach, leaders are making growth decisions with half the picture.

Marketplaces are growing faster than D2C channels. Social platforms are increasingly becoming commerce platforms. And privacy regulations aren’t loosening.

Waiting to fix measurement doesn’t just mean missing sales, it means building a media plan on flawed assumptions. If TikTok’s role is underestimated, budgets will shift to channels with more apparent last-click value but potentially less real growth impact.

Devlin stressed that “measurement is upstream of the decisions you can take.” Without the right inputs, even the most sophisticated marketing strategy will drift off-course.

For CMOs and performance leaders, the eTail Boston session offered a clear framework for addressing the blind spot:

If the $200B blind spot is closed, marketers stand to redirect significant budget towards growth-driving activity that’s currently undervalued. That means protecting demand-generation campaigns from short-term cuts, maintaining visibility in crowded marketplaces, and sustaining healthy acquisition pipelines even in tougher markets.

As Devlin summed up, “Without the data points, you’re constrained in the investments you can make.” The inverse is also true: when you have the full picture, growth decisions become not just clearer but more confident.

Fospha’s full Halo analysis, including the data behind these case studies, is available in their latest report: Halo: Measure and Grow Beyond.com. It’s a detailed look at how to end the bottom-of-funnel bias and uncover the growth potential hidden in cross-channel halo effects.

Download the report here

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