What is incrementality in marketing?
Think of it in numbers. If a campaign is followed by 1,000 sales, but 800 of those customers would have bought anyway, the campaign's incremental impact is the other 200.
It matters because many reports give marketing credit for sales it didn't create. Branded search, retargeting, and loyalty offers often reach people who were already on their way to buying. Incrementality measures the difference marketing made, which is what a budget decision depends on.
How do you measure incrementality?
The core idea is a comparison. One group is exposed to the marketing and a similar group is not. The difference in results between them is the lift that marketing caused.
| Method | How it works | Good for |
|---|---|---|
| Holdout test | A random share of the audience is kept from seeing ads | Measuring a single channel or campaign |
| Geo-lift test | Marketing changes in some regions while others stay the same | Channels that can't target individuals, like TV or out-of-home |
| Platform lift study | An ad platform splits its own audience into test and control | Quick reads inside one platform |
| Marketing mix modeling | Statistics separate marketing's effect from other factors over time | Comparing every channel at once, including offline |
A common way to express the result is incremental lift: the extra conversions in the test group divided by the conversions in the control group.
What is an example of incrementality?
Retargeting that looked better than it was
A retailer's retargeting campaign shows a strong return in its attribution report, because many people who saw the ads later bought.
A holdout test keeps a random 10% of the audience from seeing the ads. That group buys at almost the same rate, so most of those sales weren't caused by retargeting. The team moves part of that budget to prospecting, where the lift is higher.
Incrementality vs. attribution
The two are often confused. They answer different questions.
| Attribution | Incrementality | |
|---|---|---|
| Question it answers | Which touchpoints came before a sale? | Did the marketing cause the sale? |
| Method | Rules or models that assign credit | Comparison with a control group or model |
| Counts sales that would have happened anyway | Often, yes | No, that's what it removes |
| Best used for | Day-to-day optimization | Deciding whether a channel deserves budget |
Why does incrementality matter?
Budgets should go where marketing makes a difference. Without measuring incrementality, teams can keep funding channels that look efficient only because they reach people who were going to buy anyway.
- Better allocation. Money moves toward channels that create demand, not just capture it.
- Credibility with finance. A causal result is easier to defend than a credit-assignment report.
- Fewer blind spots. Channels that attribution undervalues, like upper-funnel video, get a fair hearing.
How does Alli do this?
Alli by PMG's Scenario Planner, which pairs media response modeling with Alli Brand Equity signals, approaches the incrementality question through modeling. Two-stage estimation separates the direct effect of marketing from the accumulated value of brand, so teams can see what media drove directly and what brand strength contributed.
Teams then test budget shifts in a live environment and see the likely revenue impact before committing spend. Forecasts are modeled estimates, not guarantees, and many teams keep their existing tests alongside them.
Explore Alli Scenario PlannerIncrementality FAQ
What is incrementality testing?
Incrementality testing is an experiment that compares a group exposed to marketing with a similar group that was not, to measure how much extra result the marketing caused.
How do you calculate incremental lift?
Subtract the control group's conversion rate from the test group's, then divide by the control group's rate. The result is the percentage of extra conversions the marketing caused.
What is the difference between incrementality and attribution?
Attribution assigns credit to the touchpoints that came before a sale. Incrementality measures whether the marketing caused the sale at all, by comparing against what would have happened without it.
What is incremental ROAS?
Incremental ROAS is the revenue caused by marketing, not all revenue that followed it, divided by the spend. It's usually lower than reported ROAS, and it's a better guide for budget decisions.
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