Attribution
Incrementality
The true causal lift in conversions directly attributable to advertising. It measures what would NOT have happened without ad exposure. The gold standard of attribution accuracy because it answers the fundamental question: did this ad actually cause this sale, or would the customer have bought anyway? Measured through controlled experiments like holdout tests, geo-lift studies, and conversion lift studies. Without incrementality measurement, you're optimizing toward a number that includes conversions your ads didn't cause.
Why it matters
It separates advertising that caused a purchase from advertising that was present at one. Retargeting and branded search are where the gap is widest, and both are usually the last budgets anyone cuts.
In practice
Run a holdout on the channel you are most confident about. Confidence is generally where the overclaim is largest, because nobody tests what they already believe.
Related terms