references/theories/incrementality-ladder.md

# Incrementality Evidence Ladder

## Theory

Use this as an applied decision model, not as proof that the model is correct in every market.

## Use when

- When a decision asks what marketing caused rather than what it correlated with.

## Mechanism

Choose among randomized holdouts, geo tests, lift studies, quasi-experiments, MMM, modeled counterfactuals, and attribution according to decision stakes and feasibility.

## Applied marketing use

Route the diagnosis to the specialist agents and skills connected in `neural/graph.json`; verify current platform facts using `references/2026/causal-measurement-2026.md`.

## Failure modes

- Treating a current platform feature as a permanent law of marketing.
- Selecting the theory because it sounds modern rather than because it explains the observed constraint.

## Related principle

- `counterfactual-before-credit`

## Sources

- `source:iab-state-data-2026`
- `source:google-meridian-ga360-2026`
- `source:meta-ai-ads-2026`