Incrementality testing vs MMP last-touch ROAS: stop trusting the dashboard alone

Incrementality testing vs MMP last-touch ROAS: stop trusting the dashboard alone

Your MMP shows ROAS per source. It can't tell you which installs would've happened anyway.

MMP last-touch ROAS
— ✓ Granular, per-campaign, per-creative, real-time
— ✓ Great for tactical bid and creative decisions
— ✗ Over-credits retargeting and brand search, hides organic cannibalization

Incrementality (geo-holdout / PSA / ghost ads)
— ✓ Measures true lift over a control, exposes wasted spend
— ✓ Settles "is retargeting actually working" arguments
— ✗ Slow, needs scale for significance, hard on small budgets

Use last-touch ROAS daily for tactics. Run a quarterly geo-holdout on your biggest line items to recalibrate which channels actually drive incremental installs, then reallocate.

Verdict: MMP ROAS for daily ops, periodic incrementality tests to catch the spend that's lying to you.
Best for: teams whose retargeting ROAS looks suspiciously perfect.