2023-07-18-世界银行-不完全市场下的消费者剩余_在储蓄和小额信贷中的应用_60页_5mb

Policy Research Working Paper 10481: Consumer Surplus with Incomplete Markets – Applications to Savings and Microfinance

This paper by John Loeser examines household welfare gains from financial technologies like savings and microfinance, addressing gaps in standard economic models due to incomplete financial markets. Key points:

Summary of Findings

• Consumer Surplus Measurement: Welfare gains from financial inclusion are linked to compensated demand elasticity, defined as the dynamic area under demand curves adjusted for intertemporal income effects.
• Application Analysis:
  • Retirement Savings: High-interest treatments show large demand elasticities (~-4.2), indicating significant saver surplus (~$24 per $100 deposited).
  • Commitment Savings: Price decrease elasticity (~-9.7) suggests modest gains ($~$10 per $100 deposited), but statistical imprecision limits reliability.
  • Microfinance Loans: Elasticities (~-6.4 to -14.1) grow over time, yielding substantial borrower surplus (~$15.6 per $100 loaned in early years).

Key Methodological Insights

• Dynamic Model: A micro-founded household model accounts for incomplete markets, consumption smoothing, default risks, and time-varying demand.
• Compensated vs. Uncompensated Demand: Compensated demand (controlling for income effects) provides welfare measures, while uncompensated demand (faster to estimate) often approximates consumer surplus due to high elasticities.
• Robustness Checks: Income effects bound welfare measures, but statistical uncertainty often swamps theoretical errors from uncompensated demand approximations.

Policy Implications

• Large aggregate gains exist from financial inclusion despite modest gains per unit (~1-2% of GDP potential), but precise measurement requires better price elasticity data (e.g., via large variation in interest rates).
• Unobservable heterogeneity and dynamic responses complicate aggregation, urging caution in cross-study comparisons.

Conclusion: The framework emphasizes dynamic demand elasticities for welfare analysis in developing contexts, highlighting trade-offs between measurement precision and theoretical robustness.