Theory / Model — Minimal to Carry One Insight (aeri-theory-model)

When to trigger

• A theory paper's single result (a theorem, an impossibility, a sharp comparative static) needs a tight model
• An empirical paper carries a structural or conceptual model that has grown beyond what the result needs
• The model section is eating the word budget that the result and identification need
• A referee might ask "why all this machinery for one point?"

The AER: Insights modeling discipline

AER: Insights rewards a single, surprising, clean theoretical or modeling insight delivered with the smallest model that produces it. The question is never "is the framework general?" but "what is the most economical model whose one result is important and surprising?" Generality, extensions, and robustness of the modeling go to the Supplemental Appendix; the main text states the assumptions, the one key result, and the intuition. A theory paper here is short and pointed, the opposite of a foundational framework paper for AER or a field journal.

Two cases

Case 1: The paper IS the theory (a theory short paper)

• One headline result. A single theorem, impossibility, or characterization that overturns or sharply refines a believed claim. State it early, prove it economically.
• Minimal assumptions. Strip to the assumptions the result actually needs; flag which are substantive vs. technical.
• Intuition before proof. Give the one-paragraph mechanism that makes the result memorable; full proofs to the appendix if long.
• Surprise stated. Name the prior intuition the result violates — that is why it is an AER: Insights paper, not a field-theory note.

Case 2: The model SUPPORTS an empirical insight

• Justify the model's job. It exists to deliver one object (an identifying restriction, a counterfactual, a structural parameter the data identify). Cut anything not in service of that.
• Minimal structure for identification. Tie the key parameter to a data moment (aeri-identification Branch C); keep solution/estimation detail in the appendix.
• One counterfactual, if any. If the structure delivers a counterfactual, report the single one that matters with its uncertainty; alternatives to the appendix.

What stays in vs. goes to the appendix

Word budget for the model section

The model competes with identification, result, and discussion for the same ≤7,000-word (minus exhibits) budget (aeri-writing-style). A useful rule: the in-text model should be sketchable on a single page — assumptions, the one result, the intuition. If the derivation cannot be sketched that compactly, the full version belongs in the Supplemental Appendix with only the statement and intuition in-text. A theorem environment plus a one-paragraph proof sketch is often the right in-text footprint for a theory short paper.

Worked vignette (illustrative)

A fictional theory paper proves that, under a mild condition, certification fee structure is irrelevant to information transmission. The AER: Insights version states the model in half a page (a sender, a certifier, two fee regimes), states the irrelevance result, and gives the one-paragraph intuition (the certifier's incentive constraint is unchanged by who pays). The full proof, the regularity conditions, and two generalizations go to the Supplemental Appendix. The surprise — that a policy lever people assume matters does not — is what makes it a single-insight AER: Insights paper rather than a general mechanism-design framework for a field journal.

Checklist

• The model delivers one headline result / object, stated early
• Assumptions stripped to what the result needs; substantive vs. technical flagged
• One-paragraph intuition present; long proofs/derivations to the appendix
• (Theory) the prior intuition the result violates is named
• (Empirical support) the model's single job is explicit; extras cut
• Model section does not crowd out the result and its identification within the cap

Anti-patterns

• A general framework with the AER: Insights result as a corollary buried inside
• Extensions and generalizations kept in-text "for completeness"
• A model more elaborate than the single insight requires
• Proofs in the main text that could sit in the appendix without loss
• (Empirical) structural machinery whose only output the reduced form already gives

Output format

【Case】theory-is-the-paper / model-supports-empirics
【Headline result/object】<one theorem / restriction / counterfactual>
【Minimal assumptions】<the few that matter; substantive vs technical>
【Intuition】one paragraph
【To the appendix】proofs / extensions / generalizations / robustness
【Next step】aeri-robustness