2024-06-23-美联储-需求的不确定性_选择和交易（英）_51页_658kb

报告摘要

Demand Uncertainty, Selection, and Trade
Erick Sager & Olga A. Timoshenko (Federal Reserve Board & Temple University, 2024)

Uncertainty Amplifies Trade Elasticities: Demand uncertainty increases the partial elasticity of trade flows with respect to variable trade costs in most cases (80%), driven by the dispersion effect of unexpected demand shocks.
Dual Channels of Impact:
- Selection Effect: Uncertainty lowers export entry thresholds (e.g., a 8% average dampening effect under complete information).
- Dispersion Effect: Unexpected demand shocks widen firm size distributions, amplifying elasticities but with a modest effect (e.g., 2–3% on average).
Heterogeneous Effects:
- Elasticity amplification is higher in industries with greater substitutability (e.g., complements vs. substitutes).
- Policy uncertainty tradeoffs arise: some policies dampen elasticities, others amplify them.
Incumbents Drive Trade: Endogenous selection mechanisms account for only 2–3% of total elasticities, reinforcing that incumbent firms dominate trade responses.

Model: Modified Melitz (2003) framework with demand uncertainty (idiosyncratic demand shocks), introducing selection and dispersion effects.
Data: Brazilian firm-level exports (1997–2000), cleaned to avoid measurement errors and outliers.
Estimation: Uses quantity and sales data to recover export selection shocks and shape distributions (e.g., Double Exponential Moving Gaussian for flexibility).

Partial Trade Elasticity: Elasticity of trade flows w.r.t. variable trade costs.
Endogenous Selection: Changes in exporter entry/exit margins due to demand/uncertainty.
Selection and Dispersion Effects: Two mechanisms through which uncertainty influences trade elasticities.

New estimates suggest uncertainty fundamentally alters trade elasticity properties.
Findings inform trade policy models, emphasizing the role of uncertainty under incomplete information.

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