aer-identification

# AER Identification ## Overview In AER-track empirical economics, **identification is the paper**. This skill routes among canonical designs, modern defaults, and referee-facing diagnostics. If the design is fragile, return to `aer-topic-selection`; writing cannot save it. ## When to Use - Designing the empirical strategy for a new project - The current strategy is TWFE / first-stage F / naive RDD and the referee will flag it - A prior submission was rejected on identification grounds and the design needs rebuilding - Choosing between two candidate identification strategies for the same question ## Master Decision Tree ``` Is treatment assignment plausibly random conditional on observables? ├── Yes, by design (RCT, lottery) → run the RCT analysis; register PAP via AEA RCT Registry └── No → identification must come from variation ├── Sharp threshold in a running variable → RDD (sharp or fuzzy) ├── Discrete policy change in some units, not others, over time → DiD │ ├── Single treatment date → canonical 2×2 DiD │ └── Staggered adoption → Callaway-Sant'Anna or Borusyak-Jaravel-Spiess ├── Endogenous regressor + plausibly exogenous shifter → IV │ ├── Shifter × pre-existing exposure shares → shift-share / Bartik │ └── Single instrument → weak-IV-robust inference if F < 50 ├── One treated unit / aggregate intervention → synthetic control └── None of the above → reconsider the question ``` ## Difference-in-Differences ### C...