Incrementality

Incrementality is the causal effect of an advertising activity: the business outcomes, such as sales, that occurred because of the campaign and would not have occurred without it, measured against an estimated baseline.

The IAB/MRC guidelines define it as "the true value created by any business strategy, determined by isolating and measuring related results, independent of other potential business factors," and, for retail media, "the causal impact of marketing" (IAB/MRC, January 2024, chapter 4). IAB Europe's V2.1 standard says incrementality "measures the causal impact of marketing by identifying the additional business outcomes directly driven by a campaign or tactic, compared to what would have occurred in the absence of marketing activity," and requires any network offering it to use a method from the joint IAB and IAB Europe Guidelines for Incremental Measurement in Commerce Media (IAB Europe, V2.1). Those guidelines, published 3 November 2025, accept four approaches: experiments, model-based counterfactuals, econometric models and hybrid proxies, under three principles: credible counterfactuals, control of bias, and separation of signal from noise (IAB, 3 November 2025).

The methods are randomised holdouts, geo and matched-market tests, synthetic controls, marketing mix models and machine-learning counterfactuals; each is compared in Retail media measurement standards explained. Whatever the method, the US guidelines require disclosure of the methodology, the data used, test duration and pre-campaign holdout periods (IAB/MRC, January 2024, chapter 4).

Example: exposed loyalty members spend $12.40 per head on the category during the campaign; the randomised control spends $11.70; incremental sales per head are $0.70, and incrementality is 6%.

Related: iROAS, ROAS, closed-loop measurement, clean room.

Source: IAB/MRC, "Retail Media Measurement Guidelines" (January 2024), chapter 4; IAB and IAB Europe, "Guidelines for Incremental Measurement in Commerce Media" (3 November 2025).

1. IAB/MRC, January 2024, chapter 4
2. IAB Europe, V2.1
3. IAB, 3 November 2025