Incrementality
Incrementality is the sales an ad caused that would not have happened without it.
A platform counts each conversion it can tie to an ad view or click inside its attribution window, and that includes sales from people who would have bought anyway. The platform's own return on ad spend overstates what ads caused by the widest margin in tactics that reach people already likely to buy, such as retargeting and brand search.
The incrementality factor divides the incremental conversions a test found by the conversions the platform reported. With a factor below one, the CPA target on the platform's count sits below the real goal. A factor above one, as when a lift test reads store sales no platform sees, puts it above.
Example
With a factor of 0.6, a $150 CPA goal turns into a $90 platform target. With a factor per tested channel and campaign type in its standing instructions, the agent checks similar campaigns against that adjusted target.