The Challenge
The client, a fast-growing EU home-cleaning brand selling primarily through a major online retailer, had scaled sponsored products and on-site placements aggressively. Platform ROAS looked strong, but the commercial team suspected that much of this spend was simply shifting credit from organic and repeat buyers.
In marketplace environments, sellers can end up paying for conversions they would have happened anyway, creating a cannibalisation effect rather than genuine growth.
The client needed a causal answer on the true value of sponsored products and premium placements, and a practical way to stop waste as spend scaled.
The Solution
We designed a matched product-group holdout inside the retailer account, paired with a regional split where feasible. One set of products remained fully exposed to sponsored products and premium placements, while the matched holdout group had those placements suppressed for a 4-week test window.
Because this was a holdout design, the goal was to measure what happened when paid retail media was withdrawn from comparable products. That gave us a clearer read on how much of the reported platform performance reflected real incremental demand versus displaced organic or repeat demand.
We also segmented results by product maturity and customer type, allowing us to separate displacement on high-ranking, high-repeat SKUs from genuine incremental contribution on more competitive terms and products with room to expand reach.
The Impact
The holdout showed clear cannibalisation at the current spend level. While attributed orders remained strong, total sales barely moved in the exposed group relative to holdout, indicating that a large share of paid conversions were replacing organic demand rather than adding net growth.
Across the test window, Sponsored Products and placements drove +16% attributed orders but only +1.1% lift in total units, implying roughly 70% cannibalisation at current spend levels. The story diverged by segment: mature hero SKUs showed close to flat total lift, while mid-ranking products on competitive queries delivered +4.2% total-sales lift and +19% new-to-brand orders.
As a result, the client introduced guardrails for retail media, capping spend once products hit saturation thresholds and reallocating budget towards segments that showed measurable total lift and new-to-brand growth. Reporting also shifted from platform-attributed ROAS to incrementality-led KPIs.
Key Takeaways
Retail media can look strong in-platform while adding little net growth – Especially at high saturation, where paid demand substitutes for organic demand.
Matched product-group holdouts provide a practical causal read – They measure total outcomes rather than relying on attributed conversions alone.
The commercial unlock is guardrails – Budget should concentrate where it grows category or new-to-brand demand, and pull back where it mainly shifts credit.
Tools and Techniques
- Matched product-group holdout holdout testing with placement suppression
- Data & martech audit
- Segmentation by product maturity and new-to-brand
- SQL
- R
- BigQuery (Data warehousing)
Related services
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