Incrementality

Concept

Incrementality measures the true causal sales an ad generated above and beyond what would have happened naturally without any advertising.

Layman Explanation & Analogy

Imagine handing out coupons outside a pizza shop to people already walking in the door. They use the coupon, and your report claims 100% of those sales were "caused" by your coupon! Incrementality testing tests whether those customers would have bought anyway, proving true ad value.

Worked real-world example

You run ads in 5 cities and turn off ads in 5 similar holdout cities. If the ad cities generate 25% more total sales than the holdout cities, that 25% difference is your true incremental lift.

What people get wrong & common traps

Ad platforms take 100% credit for brand search terms (e.g. users searching for your exact company name). While the ROAS looks astronomical (15x+), the incrementality is often near zero because those customers were already looking for you.

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