<b>Incrementality vs attribution: when to stop trusting last-click</b>

<b>Incrementality vs attribution: when to stop trusting last-click</b>
Attribution tells you who got credit. Incrementality tells you whether the spend caused anything. On in-app, where SKAN already blurs attribution, incrementality testing earns its keep.

✓ Geo-holdout and PSA/ghost-bid tests reveal true lift attribution can't
✓ Catches walled gardens claiming organics they didn't drive
✗ Needs scale and clean test/control design — small budgets get noisy results
✗ Most MMPs bolt on incrementality weakly; dedicated tooling (Meta Conversion Lift, Google's lift, INCRMNTAL) does it properly

The trap: running an incrementality test on a source too small to reach significance, then trusting the noisy result over your gut.

Where it pays: validating your single biggest line item, where a 10% over-attribution is real money.

<b>Verdict:</b> use incrementality to audit your largest sources; keep attribution for day-to-day optimization.
<b>Best for:</b> growth leads with budget large enough to run clean holdouts.