How can it be determined whether a coupon created new sales?

By comparing two comparable groups over the same period: one exposed to the code and one not. The difference in their purchase rates estimates the incremental sales. Where separating the groups is impossible, at least compare the purchase rate of returning users during the campaign with equivalent earlier periods, to separate existing demand from newly created demand.

Coupon Analysis

Intermediate

Updated Jul 11, 2026 Shahin editorial 2 min read

PronunciationEN/ˈkupɑn əˈnæləsɪs/

Coupon analysis is the study of who a discount code actually converted, and whether it created new sales or merely discounted sales that would have happened anyway.

The central question is incrementality, not how many codes were redeemed. Three measures make sense together: the redemption rate, the discount depth per order, and the later behaviour of coupon buyers compared with non-coupon buyers. The third matters most, because a shopper who only arrives with a discount tends to wait for the next one and to place smaller orders. The common error is crediting all discounted sales to the campaign, when a large share of those orders come from people who searched for a code at the payment step and would have bought regardless. Comparing two similar groups, one with access to the code and one without, is the only way to approach a defensible answer.

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