What is an incrementality factor?
How is it used?
Divide what the test found by what the platform reported. A factor of 0.5 means the test found half the platform's number. Then apply it to later reporting.
Common Thread Collective, which sells growth and measurement work, uses its own factors in an ad spend benchmark: iROAS = platform ROAS × factor2. Its factors come from its own geo-holdout tests and media-mix models. That is a conversion, not a definition. iROAS is still incremental revenue over ad spend.
"Naively" is the key word. The factor only travels as far as the test did.
Can it be above 1?
Yes. It can sit above or below 1. A measurement vendor's blog makes the point: platform ROAS can overstate effects by crediting people who already meant to buy, and understate them where the response happens without a trackable conversion3. The same blog says a universal correction factor is rarely defensible3. So a factor is a result, not a direction.
What must travel with a factor?
Four things, otherwise it is a number with no owner:
- Attribution window. A factor for 7-day click is not a factor for 1-day view. See attribution window.
- Channel and account. It is not portable between them.
- Test. Which design, which dates, what range. A holdout test is one source.
- Age. Markets change. Old factors go stale.
Public factors from vendors describe their own clients and tests. Ask for the range, and treat them as one vendor's data, not as a rule. A marketing-mix model can supply another view. Where incrementality is concerned, a stated source beats a round number.
For ZFD: Any factor in our calculators is an illustration. Your own tests replace it.
Worked example
Easily confused with
Incrementality factor vs iROAS
A metric. The factor is the multiplier that links the platform's report and the measured result.
Incrementality factor vs ROAS
What the platform credits, before any correction.
Incrementality factor vs Incrementality
The concept. The factor is one way to write a measured result down.
Buzzword alert
"Apply our incrementality factor"
Usually means: a correction applied to platform numbers, taken from one test in one period.
Ask: when do we re-measure it?
"Incrementality-adjusted reporting"
Usually means: reports that look tested, while the test behind them may be old or from a different setup.
Ask: what happens to our budget decisions if the factor moves?
FAQ
Is an incrementality factor an industry benchmark?
No. It is a vendor term. A factor describes one test, and it should not be copied to another account or channel.
Can I use another brand's factor?
Not safely. A factor is tied to an account, a channel and an attribution setting. Use it only as an illustration.
Is a factor the same as iROAS?
No. iROAS is incremental revenue over spend. The factor converts platform-reported results into that estimate.
Let’s find what’s actually working.
Next step. Try different factors and see what they do to your numbers. Use the Is your ROAS real? calculator.