Attribution answers which touchpoint gets credit for a sale. Incrementality answers a harder and more useful question: did the marketing cause the sale at all? A retargeting ad shown to someone who was already about to buy can receive full credit in reports while adding nothing to revenue.
How Is Incrementality Measured?
- Holdout tests: a random share of the audience is kept from seeing the ads. The difference in conversions between the exposed and holdout groups is the incremental lift.
- Platform lift studies: Meta and Google offer conversion lift tests that run this kind of holdout inside their systems.
- Geo tests: ads run in some regions and are paused in comparable ones, and sales are compared.
- On and off tests: a channel is paused for a period and the change in total sales is measured, the simplest but noisiest method.
Incremental ROAS
Incremental ROAS (iROAS) uses only the extra revenue the test shows was caused by ads: iROAS = incremental revenue / ad spend. If a campaign shows a platform ROAS of 6 but a lift test finds only a third of those sales were incremental, its real return is closer to 2.
Where Incrementality Gaps Are Usually Largest
Branded search and retargeting often look like the best performers in platform reports because they reach people who already intend to buy. Prospecting to new audiences usually looks worse in reports but is more likely to create new demand. Incrementality testing is how you find out which budget is actually growing the business.
How to Start
You do not need a data science team. Start with one question, such as whether retargeting is incremental, run a holdout or a platform lift test for a few weeks, and compare the result with blended ROAS and MER to decide where to move budget.
Frequently asked questions
What is incrementality in marketing?+
Incrementality is the additional result, such as extra sales, caused by a marketing activity compared with what would have happened without it.
What is the difference between attribution and incrementality?+
Attribution assigns credit for conversions to touchpoints. Incrementality measures whether the marketing caused conversions at all, usually by comparing exposed and unexposed groups.
How do you measure incrementality?+
With controlled tests: holdout groups that do not see ads, platform conversion lift studies, geo tests across regions, or pausing a channel and measuring the change in total sales.