The Measurement Gap: iROAS, Geo Holdouts, and Progressive Truth

Ecommerce Playbook: Numbers, Struggles & Growth · Jul 2, 2026 · 23m

Your platform ROAS is not the truth. It's a story your attribution tool tells you. Luke Austin, breaks down exactly how CTC approaches marketing measurement — and why the gap between platform-reported numbers and actual incremental revenue is where most brands make their worst capital allocation decisions.

This is Part 3 of the CTC Canon Series — our codified methodology across the core disciplines of ecommerce growth. In this episode, Luke covers the full measurement framework: why geo holdout tests are the gold standard, how CTC's database of hundreds of incrementality tests gives every new…