Incrementality
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In short
The sales a channel or partner actually caused, as opposed to the sales it was credited with that would have happened anyway.
What it means
Incrementality is the difference between what happened with a channel running and what would have happened without it. Credited sales count every order a partner touched; incremental sales count only the ones it caused. It's measured with a controlled test that switches the channel off for a comparable group of shoppers or regions and compares the results.
On your store
Your cashback partner is credited with a few hundred orders a month. You switch it off in half your regions for six weeks, and sales there barely move. Most of those orders weren't incremental.
Why it matters
PartnerCentric, an agency that sells attribution technology, found coupon, loyalty and cashback partners started only 13% of the conversions credited to them across its clients in late 2024.[PartnerCentric, Feb 2025] (opens the source) A large field experiment at eBay found its brand-keyword search ads had no measurable short-term benefit, because the people who clicked were often going to buy anyway.[NBER (Blake, Nosko and Tadelis), May 2014] (opens the source) 60% of US senior decision-makers in a survey by Haus, which sells incrementality testing, trusted independent incrementality testing most among measurement methods.[EMARKETER (Haus survey), May 2026] (opens the source)
Sources
- 1PartnerCentric, “Next-gen affiliate performance measurement: PartnerCentric leads the transparency movement”, Feb 2025. silicon.co.uk (opens the source)
- 2NBER (Blake, Nosko and Tadelis), “Consumer heterogeneity and paid search effectiveness: a large scale field experiment”, May 2014. nber.org (opens the source)
- 3EMARKETER (Haus survey), “Incrementality testing earns marketers' top trust”, May 2026. emarketer.com (opens the source)
Read next
Related terms
- Holdout testAn experiment that leaves a random group of shoppers without a change, so the difference against everyone else shows what the change did.
- Last-click attributionA crediting rule that gives the whole sale, and the whole commission, to the last affiliate whose link the shopper clicked before buying.
- Coupon-extension trafficThe store sessions in which a coupon or cashback extension was active, measured apart so you can see what those shoppers buy and what they pay.
- Cashback extensionA browser add-on from a cashback or rewards site that pays shoppers part of the affiliate commission a store pays on their order.
