Sam’s Club Just Shipped the Rest-of-Market Measurement the Industry Said Was Missing

On April 16, Sam’s Club detailed the 2026 roadmap for its Member Access Platform, the retail media network it rebranded as the industry’s first Retail Experience Network in April 2025. The update covers five named initiatives: Expert Review Videos on product detail pages, tablets at in-club demo carts for on-the-spot ratings and reviews, a MAP Influencer Program tapping Sam’s Club’s Creator Network, an integration with Meta that runs Sam’s Club member audiences through a LiveRamp clean room, and MAP Rest of Market Analysis, a measurement product built on Circana’s multi-outlet panel of more than 500 million loyalty cards.

Four of those five are operational upgrades to experiences Sam’s Club already runs. The fifth is the one suppliers should be reading most closely.

The industry has been asking for rest-of-market measurement for at least a year

Writing in January 2025, the Path to Purchase Institute described rest-of-market impact as the next critical step in retail media measurement. P2PI’s argument was that without linkage to a total-market conversion panel, retailers and brands could not answer whether a campaign had halo effects beyond the retailer’s own channel. The piece named Circana, NCS, and Numerator as the panels capable of providing that linkage. Retailers had not shipped the product yet.

Sam’s Club has now shipped it. According to the company’s announcement, MAP Rest of Market uses the Sam’s Club membership model and deterministic member IDs, joined to Circana’s panel, to measure incremental sales, incremental return on ad spend, and new buyer acquisition at retailers other than Sam’s Club. Sam’s Club reports that campaigns using ROM show a median 17 percent lift in incremental ROAS compared to measuring Sam’s Club performance alone. The company did not disclose sample size, category mix, or whether that median reflects pilot campaigns or general availability.

The 17 percent figure implies that single-retailer measurement has been understating campaign value

If ROM campaigns show a 17 percent median iROAS lift over Sam’s Club-only measurement, the straightforward reading is that suppliers measuring Sam’s Club performance in isolation have been undervaluing their Sam’s Club media spend by roughly that amount on average. That is useful for MAP to disclose because it gives sales teams an argument to bring into annual planning conversations: your Sam’s Club media investment is doing more work than your dashboard shows.

The less comfortable reading is what ROM means for brands that have been over-indexing on Sam’s Club in their retail media mix because Sam’s Club-only measurement made Sam’s Club look like their best-performing network. If ROM exposes that performance at other retailers was being driven partly by Sam’s Club exposure, it also exposes the inverse: some of what looked like Sam’s Club iROAS was actually cross-retailer spillover being double-counted. Suppliers should ask MAP for methodology disclosure on how ROM separates Sam’s Club-attributable lift from lift that would have occurred without Sam’s Club exposure.

Measurement products from retailers are not neutral

There is a structural issue worth surfacing. Retailer-supplied measurement products are measurement products sold by the entity whose ad inventory they evaluate. MAP has every commercial incentive to show that campaigns on its network drive incremental sales beyond its four walls. That does not make the ROM numbers wrong. It does mean suppliers should not adopt ROM as their baseline cross-retailer measurement without independent validation.

A disciplined approach would be to run ROM alongside an existing marketing mix model or a third-party incrementality study for at least two full quarters before treating ROM output as decision-grade. P2PI’s 2025 piece on measurement explicitly warned about the difficulty of reconciling retailer-level audience metrics with market-level marketing mix model outputs. That problem does not disappear because the retailer now offers its own market-level view.

The other four features are incremental additions to a stack that has been building since 2023

The April announcement lands on top of a two-year arc of MAP capability expansion. Chain Store Age reported that Sam’s Club added display ads to its Scan & Go mobile self-checkout in July 2024, began offering full-funnel video advertising onsite, in-app, and offsite in December 2023, and released Omni-Impact in June 2025 to let advertisers see incremental sales across all MAP channels. Progressive Grocer reported in April 2025 that MAP had already introduced Brand Lift, Multi-Touch Attribution, Customer Lifetime Value, and propensity modeling with signal fidelity as part of the Retail Experience Network rebrand.

Against that backdrop, the four non-ROM initiatives announced on April 16 are incremental rather than foundational. Expert Review Videos embed credible video content, such as the licensed physical therapist featured on GhostBed’s product page, directly into the product detail experience. Sam’s Club reports that combined with MAP media, the video approach delivered approximately 4x sales lift on GhostBed. That is a single campaign result and should be treated as such, but it points at a real supplier tool: third-party expert validation embedded where the purchase decision happens.

The demo cart tablet program turns in-club sampling into a ratings-and-reviews capture event, tied to membership ID, with reviews automatically published to the product detail page. For categories where in-club sampling is already part of the mix, this closes a measurement gap that has existed since in-club demos became a standard promotional tactic. Suppliers running demo programs at Sam’s Club should be asking their MAP representative how this changes what they can measure and attribute.

The MAP Influencer Program brings Sam’s Club’s Creator Network into paid campaign execution, with closed-loop measurement tying creator content to in-club and online sales. Creator content programs run by retailers are a growing trend across the retail media landscape. The distinguishing feature here is the deterministic attribution back to member purchases.

The Meta integration extends deterministic member targeting into the two highest-volume social platforms while preserving closed-loop measurement. For suppliers already running Meta campaigns to shopper audiences, this removes a layer of probabilistic modeling. It also fits the multi-touch attribution architecture MAP has been building out, letting brands see how Meta exposure interacts with onsite, offsite, and in-club touchpoints in a single view.

The supplier question this raises is a resource question

The five initiatives do not require equal attention. Expert Review Videos, demo cart tablets, the Influencer Program, and the Meta integration are campaign-execution decisions that can be piloted within existing Sam’s Club media budgets. Suppliers who run Sam’s Club retail media should work through them with their MAP representative as part of normal 2026 planning.

ROM is different. ROM is a measurement product that, if adopted, changes how suppliers evaluate Sam’s Club spend against every other retail media network in their mix. That changes budget allocation, not just campaign tactics. The suppliers best positioned to evaluate ROM are those with existing marketing mix model capabilities and third-party measurement partners who can independently validate what ROM shows. The suppliers most at risk of accepting ROM output uncritically are those who lack those capabilities and are relying on retailer-supplied dashboards as their primary measurement view.

That second group is substantial. Adweek reported in March 2026 that Sam’s Club is positioning MAP as a strategic growth engine rather than an ad platform, with closed-loop data as the core differentiator. The framing is accurate. But a growth engine whose speedometer is provided by the engine’s manufacturer is a speedometer that should be calibrated against a second instrument.

What to watch between now and Q3 planning

Three developments will determine how ROM lands with the supplier community. The first is whether Sam’s Club publishes methodology disclosure on how ROM attributes lift, the sample size behind the 17 percent median figure, and the category breakdown. The second is whether independent measurement firms, including Circana in its non-MAP capacity, publish validation studies or challenge papers on ROM outputs. The third is whether other retail media networks, specifically Walmart Connect, Kroger Precision Marketing, and Amazon Ads, respond with comparable rest-of-market products. If they do, cross-retailer measurement becomes a competitive feature rather than a Sam’s Club differentiator, and the ROM numbers become one data point among several rather than the source of truth.

None of that is likely to be resolved before Q3 planning cycles begin. Suppliers making Sam’s Club budget decisions for the back half of the year will do so with ROM on the table and without independent validation of what it shows. That is the actual decision point, and it is worth treating as one.

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