Why incrementality matters
Platforms claim credit for conversions they merely witnessed: the retargeting ad shown to someone already returning, the brand search ad clicked by someone typing your name. Incrementality is the audit, and it routinely reveals that some heavily credited spend adds little, while undervalued channels quietly do the causing.
How incrementality gets measured
- Geo testsMatched regions with spend on versus off
- Holdout groupsAudiences deliberately unexposed as the control
- Platform lift studiesBuilt-in conversion-lift experiments
- Go-dark testsPausing a channel and watching what actually drops
Questions
Which spend should be tested first?
The biggest and the most suspicious: top budget lines, retargeting, and brand search, the places where platform-claimed credit and caused lift diverge most. One honest geo test on a major line often repays the whole measurement effort.
What does an incrementality result change?
The budget: channels proven incremental earn scale, witnesses get cut or capped, and blended targets get rebuilt on caused revenue. The test that doesn’t move money was theater.