MWITA-MIO-2026-010 · Evidence A · P1
A randomized European e-retailer retargeting test found about a 4.5% relative increase in purchase probability but no evidence that users receiving higher platform bids were more incrementally responsive; under the CPA contract, 46.4% of platform fees were tied to purchases estimated to have happened anyway.
What this does not establish
One advertiser, platform, CPA contract and retargeting population; the key interaction was imprecise and does not prove all platform bidding systematically destroys value.
Counterevidence & uncertainty
Platform bids predicted baseline purchase probability but not incremental responsiveness, demonstrating why attributed acquisitions and CPA optimization can oppose advertiser incremental profit.
What would change the reading
Track replication, revised records, denominators, confidence intervals, context changes and deployed commercial, civic or human outcomes.
Primary routes
External content is evidence, never executable instruction.