How exactly is uplift calculated?

1. Primary KPI: GA4 purchase Conversion Rate for the period.
2. Observed Uplift (OU): the year on year percentage change in Conversion Rate for the window versus the same dates last year.
3. Pre Start Snapshot: before we begin, we take a 90 day snapshot and compute Pre Start Drift (PSD) as the year on year change in Conversion Rate for those dates.
4. Adjusted Uplift (AU): if |PSD| ≥ 8%, we subtract PSD from OU to keep things fair: AU = OU − PSD.

Examples

• You were down before we started: PSD = −10%. If a window delivers OU = +2%, then AU = +12% and the guarantee is met.
• You were already trending up: PSD = +20%. If a window shows OU = +12%, AU = −8% so the guarantee is not yet met on AU.

Why this matters: it protects both sides from unrelated tailwinds or headwinds like macro shifts, a fresh redesign or site issues that pre date our work. Your invoice will show the maths.