| name | aejmic-theory-model |
| description | Use when the model setup, equilibrium concept, or proof architecture is the bottleneck for an American Economic Journal: Microeconomics (AEJ: Micro) manuscript — the central skill for a theory-first paper. Builds the model to the AEJ: Micro bar (clean, general, well-motivated result); it does not check whether your theorem is correct. |
Theory Model & Proof Architecture (aejmic-theory-model)
This is the central skill for AEJ: Micro. The journal is theory-first: the deliverable is a clean, general, well-motivated result — a theorem, characterization, or impossibility — that a broad microeconomics audience finds illuminating. Get the model and the proof right before anything else.
When to trigger
- The primitives (players, actions, information, timing, payoffs) are not yet pinned down
- The equilibrium / solution concept is unstated or mismatched to the question
- A result is conjectured but the proof strategy is unclear or fragile
- You are trading generality against tractability and cannot decide where to cut
- A referee questions which assumption the result actually depends on (then pair with
aejmic-identification)
The AEJ: Micro modeling bar
AEJ: Micro wants the economics to be the point: the model should be the simplest environment in which the mechanism is visible, and the result should travel beyond the example. It sits between JET/GEB (specialist, often maximal generality) and AEJ: Applied (empirical). Aim for a result that a non-specialist micro theorist can state in one sentence and that a specialist finds non-obvious.
1. Model setup — make primitives minimal and motivated
- State players, action sets, information structure, timing, and payoffs explicitly; flag every assumption that is substantive vs. WLOG.
- Prefer the minimal environment that exhibits the mechanism; add structure only when it earns its keep in the result.
- Motivate each non-standard assumption economically (an institution, a friction), not just for tractability.
2. Equilibrium / solution concept — name it and justify it
- Pick the concept that matches the question: Nash / subgame-perfect / sequential / PBE; dominant-strategy or Bayesian incentive compatibility (mechanism design); stability / core (matching, market design); rationalizability or level-k (behavioral).
- State existence and, where it matters, uniqueness (or characterize the equilibrium set). Refinements should be justified, not invoked to rescue a result.
3. Proof strategy — choose the architecture before writing it
- Common architectures: construction (exhibit the object), revelation principle then optimize over direct mechanisms, fixed-point / monotone-comparative-statics (Topkis, single-crossing), duality / LP (information design, Bayesian persuasion), induction on type/stage, variational / first-order arguments, impossibility by contradiction.
- For a characterization, prove both directions; for an optimum, verify the candidate is global (not just a local/first-order point).
4. Generality vs. tractability — decide deliberately
- A finite/binary type space that exposes the mechanism cleanly often beats a continuum that buries it. State the cost: what does the simplification rule out?
- If the general case is the contribution, prove it generally; if the insight is the contribution, prove it where it is cleanest and discuss extension in
aejmic-robustness.
5. Where proofs live
- Short, illuminating proofs (or proof sketches) in the main text; long or routine proofs in the appendix. The main paper should be self-contained for the key results — do not hide a load-bearing proof in supplementary material.
Checklist
Anti-patterns
- A model loaded with assumptions, several only for tractability, none flagged — the mechanism is invisible
- Asserting an equilibrium without existence, or invoking a refinement only to rescue the result
- "It can be shown that…" standing in for a proof of a load-bearing claim
- Maximal generality that obscures the economic point (reads as JET, not AEJ: Micro), or a one-off example with no result that travels
- A first-order condition presented as if it established a global optimum
Worked vignette: a screening result (illustrative)
A monopolist screens buyers with private values. A weak setup throws in a continuum of types and three frictions at once; the optimal-contract characterization becomes a thicket. The AEJ: Micro move: start with two types, derive the standard "no distortion at the top, downward distortion below" characterization as a clean Proposition, prove it by the relaxed-program-then-verify-monotonicity architecture, then in aejmic-robustness show the continuum case preserves the qualitative result. The two-type model is the simplest environment where the distortion is visible — and the result travels.
Output format
【Model】players / actions / information / timing / payoffs (substantive vs. WLOG flagged)
【Solution concept】[Nash/SPE/PBE/IC/stability/…] + existence/uniqueness
【Main result】Proposition stated in words
【Proof architecture】[construction / revelation+optimize / fixed-point / duality / induction / impossibility]
【Generality call】where proved + cost of any simplification
【Proofs live】main text: [...]; appendix: [...]
【Next step】aejmic-identification (what makes it tight) or aejmic-robustness (extensions)
Supplementary resources
