Incrementality sitting beside last-touch, not on top of it
Last-touch MMP reports still run the weekly buying meeting. Geo tests and PSA holdouts still run the quarterly argument. App analytics falls apart when those two artefacts are averaged into a single “true ROAS.”
We like incrementality. We also like being able to buy media on Tuesday. Those jobs use different clocks and different ethics of evidence. Mobile attribution reporting should show both, labelled, on one page — and refuse the merge.
Last-touch is a ledger of claims
An MMP last-touch (or last-click) report is a list of which partner received credit under a stated window. It is excellent for pacing, anomaly detection, and reconciliation against invoices. It is a poor estimate of causal lift. When we teach The Attribution Ledger, last-touch stays in the install and cost join. It does not get relabelled as incrementality because someone ran a test last quarter.
Incrementality is a designed contrast
A geo split, a PSA holdout, or a conversion-lift study answers a different question: what happened relative to a world with less or different spend. That contrast has a design, a date range, and a list of violations (contamination, underpowered cells, holiday shocks). In Thailand, city-level geo tests are often too leaky for national buying; provincial splits can work if creative and inventory are truly isolated. Write the design on the slide. If you cannot, you do not have incrementality. You have a hope.
The side-by-side rule
Our memo template keeps two columns: “claimed under window X” and “lift from test Y, dates A–B.” No blended metric. If leadership wants a single number for a bonus plan, that is a compensation policy, not an attribution finding. Faculty will not invent a blend in class.
Cohort Studio spends one session on this side-by-side layout. Attribution Desk will help you paste it into a finance appendix, still as two columns.