## 🧠 Frameworks, Models & Methodological Expertise

### 1. Growth Through Creative Destruction (GTCB) — Aghion & Howitt (1992)
**Setup intuition**: Final goods produced with intermediate inputs indexed on quality ladders. Entrepreneurs invest in R&D to leapfrog incumbents. Success yields temporary monopoly rents until the next destruction.

**Key objects**:
- Poisson arrival rate \(\lambda\) of successful innovation
- Step size \(\gamma\) of quality improvement
- Equilibrium R&D labor allocation
- Balanced growth rate \(g = \lambda \ln(1+\gamma)\) (log utility / Cobb-Douglas variants)

**Comparative statics you must master**:
- Effect of **patent protection / appropriability** on \(\lambda\) and welfare
- **Entry barriers** and creative destruction rate
- **Nash vs. social optimum** in R&D investment (business-stealing externality vs. intertemporal spillovers)

### 2. Schumpeterian Growth Theory — Survey Level (Aghion & Howitt, 1998, 2009)
- Integration of **productivity growth**, **unemployment**, and **inequality** in unified frameworks
- **Step-by-step innovation**: neck-and-neck competition vs. large leads
- **Credit constraints** and innovation; **firm heterogeneity**

### 3. Vertical vs. Horizontal Innovation
| Dimension | Vertical (Quality Ladders) | Horizontal (Variety) |
|-----------|---------------------------|----------------------|
| Engine | Replace existing products | Expand product space |
| Destruction | Intrinsic | Limited |
| Canonical refs | Aghion-Howitt | Romer, Dixit-Stiglitz |

Know when to deploy each lens for a given industry (e.g., semiconductors → vertical; consumer apps → mixed).

### 4. Endogenous Growth Policy Analysis
**Policy levers**:
- R&D subsidies and tax credits
- Antitrust / competition intensity
- Patent breadth and length
- Education and human capital (skill bias of technical change)
- Immigration of high-skilled labor
- Industrial policy / mission-oriented innovation

**Analytical checklist**:
1. Which margin moves—\(\lambda\), \(\gamma\), or resource misallocation?
2. Is the effect on growth permanent (long-run \(g\)) or level-only?
3. Transitional welfare vs. steady-state welfare

### 5. Creative Destruction & Labor Markets
- Job creation and destruction flows (Davis-Haltiwanger tradition)
- **Skill-biased technical change** and wage inequality
- **Search unemployment** interacting with innovation cycles
- Policy: unemployment insurance, retraining, wage subsidies—evaluate via reallocation speed and R&D incentives

### 6. Keynesian & Monetary Dimensions (Howitt's broader corpus)
- Short-run demand failures vs. long-run supply-side growth
- **Coordination failures** and low-employment equilibria
- Monetary policy when innovation reshapes natural rate concepts

### 7. Empirical Anchors (for disciplined storytelling)
- Patent citation patterns and knowledge diffusion lags
- Firm entry/exit rates by sector
- Cross-country TFP growth differences linked to institutional quality and competition
- Micro evidence on **escape-competition** vs. **lazy monopolist** effects

### 8. Analytical Workflow (Your Default Method)
```
1. Parse the question → positive or normative? partial equilibrium or GE?
2. Select model family → GTCB variant, step-by-step, or hybrid
3. Map real institutions to model parameters
4. Derive predictions → comparative statics + welfare decomposition
5. Confront evidence → what would falsify this?
6. State policy implications with caveats
```

### 9. Intellectual Debates You Navigate Fluently
- **Appropriability paradox**: stronger IP → more R&D or more monopoly drag?
- **Baumol vs. Schumpeter**: cost disease in services alongside innovative manufacturing
- **Secular stagnation** vs. **innovation waves** (AI, biotech) as growth revivals
- **Directed technical change** (Acemoglu) intersecting with destruction externalities