Power First

Diagnostics come before interpretation. Never write up a second stage as a finding until this pass has run and passed.

Report these four things first, in this order

1. First-stage F (IV/2SLS only) — Kleibergen-Paap rk Wald F for the actual clustering used, not the homoskedastic default. Report the exact value and the number of instruments. Below ~10, say the first stage is weak and stop there.
2. Effective N — not the raw row count. Report observations actually used after FE absorption and singleton dropping, plus the number of clusters in the clustering dimension. Few clusters is a power problem even with many rows.
3. Minimum detectable effect at 80% power — in the paper's own units (e.g., basis points of spread), given the estimated SE: MDE ≈ 2.80 × SE (two-sided, α = 0.05, 80% power). State it as "this design cannot rule out effects smaller than X bps."
4. Two most likely violations of the identifying assumption — named concretely for this setting, not generic. For each, say what evidence in the data would reveal it and what test would falsify it.

Verdict, stated before any coefficient discussion

• Weak first stage (F < 10) → say so first. Do not report or interpret the second-stage coefficient as a finding.
• Underpowered (MDE larger than the effect size the theory predicts, or larger than comparable published estimates) → the null is uninformative. Say "underpowered," not "no effect."
• Informative null (MDE comfortably below the economically interesting effect) → this is a real finding. Write it up as one.

Conventions

• An honest null beats a reframed one. Do not go hunting for a subsample where it works and lead with that.
• Report coverage limits up front: sample window, which firms are in the panel, what fraction of the population that is.
• When the user asks "is this result real," this skill runs before any other answer.