Theory & Mechanism Model (ecj-theory-model)

When to trigger

• A reduced-form result has no model or stated mechanism behind it ("what is the economics?")
• A structural/theory paper's model exists but its assumptions or comparative statics are not disciplined
• The empirical specification is not derived from, or connected to, any economic framework
• A referee will ask which economic force drives the result and you cannot point to one

Why this matters at EJ

EJ publishes the full breadth of economics — theory and applied — and both are read for whether the economic argument is sound and of broad interest. A clean empirical effect with no mechanism is a half-paper here: EJ wants to know why, not only whether, because the "why" is what travels across fields and gives the result general relevance. The model need not be elaborate; a one- or two-equation framework that delivers a sharp, testable comparative static, explained so a generalist follows it, is often stronger than a baroque one. EJ's exposition premium applies to theory too — the economic intuition is stated in words before the algebra. If the contribution is purely methodological/econometric with no substantive economics, weigh The Econometrics Journal (also RES) instead of EJ.

Two modes:

• Theory-led paper: the model is the contribution; empirics (if any) illustrate or test it.
• Empirics-led paper: a compact model or explicit mechanism organizes the empirics, generates the prediction being tested, and gives the estimate its interpretation.

Building / disciplining the model

Minimal-model discipline (for empirics-led papers)

• Write the smallest model whose comparative static is the empirical prediction. Tie one model object to one estimated coefficient.
• State agents, their objective, the constraint, and what they optimize over. The economic logic — substitution, incentives, market clearing — should be visible to a non-specialist.
• Derive the sign/shape prediction the data will test, and say what evidence would refute it.
• Check the partial-equilibrium result against general equilibrium: does the effect survive when prices/quantities adjust elsewhere? If not, say so and bound it.

Full-model rigor (for theory-led / structural papers)

• Assumptions: each one earns its place; flag which are substantive vs. technical convenience.
• Existence/uniqueness of equilibrium where relevant; comparative statics stated as propositions.
• Welfare analysis: who gains, who loses, and the efficiency benchmark.
• Map structural parameters to identifying variation before estimation (hand off to ecj-identification).
• Robustness of qualitative conclusions to the key assumptions; counterfactuals.

Consistency checks a referee runs

• Do agents in the model behave optimally given prices and incentives?
• Does the market clear, and does the result survive equilibrium adjustment?
• Are there unmodeled selection or entry/exit margins that would overturn the conclusion?
• Is the comparative static the paper tests actually a prediction of the model, or assumed?
• Does the welfare claim follow from the model, or is it asserted?
• Could a generalist economist follow the economic intuition without the appendix?

Checklist

• An explicit model or written-down mechanism exists
• One testable comparative static is derived and mapped to an estimated object
• Optimization, incentives, and market clearing are visible in the logic
• The economic intuition is stated in words before the algebra (EJ exposition bar)
• General-equilibrium / selection feedback considered (or bounded if assumed away)
• Assumptions labeled substantive vs. technical
• Welfare / efficiency implications follow from the model, not asserted
• The model is the smallest one that delivers the result (no gratuitous generality)

Anti-patterns

• An empirical result with no model and no mechanism — "we find an effect" with no economic story
• A model whose comparative statics are never connected to the data
• Partial-equilibrium conclusions that ignore obvious GE feedback a referee will raise
• A needlessly elaborate model that obscures rather than sharpens the economic point
• Algebra with no verbal economic interpretation — fails EJ's exposition bar
• Assumptions chosen for tractability that secretly drive the headline result
• Welfare statements that do not follow from the stated objective function

Output format

【Mode】theory-led / empirics-led
【Core mechanism】the economic force in one sentence
【Model primitives】agents / objective / constraint
【Testable prediction】comparative static + the estimated object it maps to
【Intuition-before-algebra】stated in words? [y/n]
【GE / selection check】survives equilibrium adjustment? [y/n + note]
【Welfare】who gains/loses; efficiency benchmark
【Next】ecj-identification (to test it) or ecj-robustness