incrementality
The extra results caused by advertising that would not have happened without it.
Definition
Incrementality asks whether a campaign actually created additional sales, rather than just claiming credit for customers who would have bought anyway. It is measured through experiments, such as holding out a group that does not see ads and comparing outcomes, or geographic tests. It is harder than reading dashboards but more reliable. Agencies that propose incrementality tests show a commitment to evidence; define the test design, duration and success rule in advance. Even a simple test, such as pausing a campaign in one region for a few weeks, can reveal how much of the reported result was truly caused by ads.
In a sentence
A holdout test measured incrementality of the retargeting campaign.
Ad platforms may overstate results compared with incrementality tests.
