The Maze: Amazon Ads can now show U.S. advertisers which rival retailers receive sales after people see an Amazon DSP campaign. That sounds like a reporting upgrade. It is really a power shift. Amazon is no longer asking brands to judge media only by what happens inside its own store. Retailer-level Omnichannel Metrics turns off-Amazon demand into a named channel map, giving brands evidence for budget allocation and partner negotiations while giving Amazon a wider view of retail performance.
Two retailers capture 42% of the measured off-Amazon sales. In the 18-week example, Walmart generates $8.28 million and Target $6.84 million. Together they account for $15.12 million of the $36 million total. Add Costco's $5.04 million and the top three reach 56%. The remaining 44% is spread across Best Buy, Sam's Club, direct-to-consumer, Home Depot, Lowe's and other retailers. Amazon's new breakout makes that distribution visible at study and campaign level.
Sales share hides very different basket economics. Walmart leads with 31,846 units at a $260 average selling price. Target follows with 24,467 units at $285. Costco produces 14% of sales from only 12,078 units because its $420 average ticket is the highest in the group. Best Buy sits at $370. The same campaign can therefore create volume in one channel and higher-value purchases in another. A single blended off-Amazon return number would hide that distinction.
This is attribution, not neutral market truth. OCM combines Amazon Shopper Panel data with third-party signals and uses exposure-based attribution to identify where ad-exposed shoppers purchased. Reporting is aggregated and anonymized, and the product can refresh while campaigns are live. But the example does not disclose the advertiser, category, spend, control group, confidence interval or incrementality. Its 23% Walmart share is a share of this measured report, not Walmart's market share and not proof that every purchase was caused by Amazon media.
The budget argument now travels beyond Amazon's checkout. A brand can show its chief financial officer that Amazon media supported sales across Walmart, Target or Home Depot, then use the same evidence in retailer conversations. That weakens the old assumption that spending with Amazon only grows Amazon. An official apparel case study found 64% of attributed purchases outside Amazon and used marketing-mix modeling as a second check. The smart operating model is not blind trust in one dashboard; it is OCM for fast channel detail, then independent validation for budget decisions.
Why it matters: Retail media has been built around walled gardens: each platform proves value inside its own walls. Amazon is now selling a broader claim—that its advertising can create demand across the whole retail landscape and name the beneficiaries. Brands gain a more complete view of media performance. Retail partners gain evidence that Amazon spend can help them. Amazon gains something even more strategic: a measurement role that reaches beyond its marketplace. The company that defines the cross-retailer scorecard gets more influence over where the next advertising dollar goes.
Sources: Amazon Ads launch | OCM product page | OCM and MMM case study
