---
name: ecj-theory-model
description: Use when a The Economic Journal (EJ) manuscript needs an explicit economic model or mechanism — either a theory paper's model, or the framework that gives a reduced-form empirical result its economic meaning. Builds and disciplines the economic argument; it does not run estimation (see ecj-identification).
---

# 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
```