Incrementality
Incrementality is the portion of conversions that advertising actually caused, as opposed to conversions that would have happened without it, measured by holding out a randomized control group.
By keeping a randomized group unexposed to the ads and comparing its conversion rate to the exposed group, incrementality isolates the causal effect. The lift between the two is what the advertising truly added, not merely what it got credited for.
It almost always reads lower than platform-reported results, because attribution counts conversions the ads would have won anyway. Incrementality is the stricter, more honest measure of whether a channel deserves its budget.
Learn this stuff by email
New definitions, tools, and explainers when I publish them. No spam, unsubscribe anytime.