Incrementality measures the true additional impact of an ad, the conversions that wouldn’t have happened without it.
To understand this clearly, think of your customers divided into two groups:
- Organic shoppers: people who already loved your brand or intended to buy. If they see your ad and buy, the ad didn’t actually change their behavior, they were going to buy anyway.
- Incremental shoppers: people with no immediate intention of buying. Seeing your ad is the exact trigger that convinces them to make a purchase.
Without measuring incrementality, standard ad platforms like Google or Meta take 100% of the credit for both shoppers, because both saw an ad before buying. Incrementality testing filters out the organic shoppers, so you only pay for and optimize toward marketing that drives true, brand-new growth.
