Incrementality & Geo-Experiments in 2026: How Many Conversions Ads Really Add
TL;DR: Incrementality shows how many conversions ads truly added on top of what would have happened anyway. The most practical method is a geo experiment — comparing regions with and without ads. Judge uplift and iROAS, not last-click attribution. Last-click attribution answers who gets credit for a conversion, but not the question that matters: how…