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（英）-2023.6-60页_5mb

Report Content Analysis Summary: Consumer Surplus with Incomplete Markets: Applications to Savings and Microfinance

Introduction

This paper addresses empirically elusive household welfare gains from financial inclusion. It establishes that household welfare gains from a financial technology are equivalent to the area under dynamically compensated demand in a household model with incomplete financial markets, general technology, preferences, and choice sets. The paper empirically estimates compensated demand for financial technologies using experimental variation in interest rates from three randomized control trials, finding that while welfare gains per dollar lent or saved are small due to large compensated demand elasticities, they correspond to large aggregate welfare gains from financial inclusion.

Model and Theory

A dynamic household model with incomplete financial markets, consumption, investment, and uncertain outcomes is developed. Key theoretical contributions include:

• Establishing consumer surplus as equal to the area under dynamically compensated demand.
• Demonstrating that changes in prices induce equivalent variation, a vector of period-state-contingent transfers that maintains utility.
• Deriving Roy's identity for dynamic settings, enabling welfare analysis under incomplete markets.

Empirical Applications

Retirement Savings (Duolo et al., 2006)

• Exploits experimental variation in retirement savings match rates in the U.S.
• Estimates a large price elasticity of demand ( ✔️ = −4.22).
• Consumer surplus ranges from $94.58 to $107.43 per $100 of deposits under the high-match treatment.

Commitment Savings (Karlan & Zinman, 2018)

• Uses experimental variation in interest rates for commitment savings accounts in the Philippines.
• Estimates a price elasticity of demand ( ✔️ = −9.74?).
• Consumer surplus ranges from $10.27 to $23.70 per $100 of deposits.

Microfinance (Karlan & Zinman, 2019)

• Leverages experimental variation in interest rates for microfinance loans in Mexico.
• Finds increasing price elasticities over time (e.g., 6.40 to 14.08).
• Consumer surplus increases from $7.10 to $15.62 per $100 of loan amount.

Policy Implications

• Implementation: The framework provides tools for policymakers to quantify welfare gains from financial inclusion.
• Support: Continued innovation and access expansion can yield substantial aggregate benefits despite small elasticities.

Conclusion

The paper introduces a novel theoretically-based approach to estimate household welfare gains from financial technologies using experimental variation in interest rates. It successfully estimates consumer surplus per dollar of financial service, finding aggregate welfare gains to be substantial despite modest elasticities per unit of service. This method serves as both a practical tool and a theoretical contribution for evaluating financial inclusion policies.