The article by Dean Karlan and Jonathan Zinman examines the impact of expanding access to consumer credit at a high interest rate (200% APR) through a field experiment in South Africa. The study uses a randomized supply decision approach to estimate the effects on borrowers. Key findings include: 1. **Credit Constraints**: The experiment confirmed the presence of binding liquidity constraints, as treated applicants borrowed more and shifted their borrowing composition towards loans from the Lender. 2. **Borrower Outcomes**: Borrowers who were marginally rejected by the Lender and subsequently approved through the randomized process showed significant improvements in overall borrower outcomes, including economic self-sufficiency, food consumption, and subjective well-being. 3. **Profitability**: The marginal loans were found to be profitable for the Lender, although less so than inframarginal loans. 4. **Methodology**: The study demonstrates the effectiveness of randomized-control trials in identifying the severity of liquidity constraints and evaluating credit access expansion efforts. The methodology also highlights how lenders can optimize their sustainability and outreach by using controlled risks through randomized experimentation. 5. **External Validity**: The findings have implications for policy and practice, particularly in markets with different competitive structures or consumer characteristics. However, the results may not apply to settings where lending is expanded through branch expansion rather than "encouragement" designs. Overall, the study suggests that expanding access to consumer credit can improve borrower outcomes, even at high interest rates, and provides valuable insights for policymakers and practitioners.The article by Dean Karlan and Jonathan Zinman examines the impact of expanding access to consumer credit at a high interest rate (200% APR) through a field experiment in South Africa. The study uses a randomized supply decision approach to estimate the effects on borrowers. Key findings include: 1. **Credit Constraints**: The experiment confirmed the presence of binding liquidity constraints, as treated applicants borrowed more and shifted their borrowing composition towards loans from the Lender. 2. **Borrower Outcomes**: Borrowers who were marginally rejected by the Lender and subsequently approved through the randomized process showed significant improvements in overall borrower outcomes, including economic self-sufficiency, food consumption, and subjective well-being. 3. **Profitability**: The marginal loans were found to be profitable for the Lender, although less so than inframarginal loans. 4. **Methodology**: The study demonstrates the effectiveness of randomized-control trials in identifying the severity of liquidity constraints and evaluating credit access expansion efforts. The methodology also highlights how lenders can optimize their sustainability and outreach by using controlled risks through randomized experimentation. 5. **External Validity**: The findings have implications for policy and practice, particularly in markets with different competitive structures or consumer characteristics. However, the results may not apply to settings where lending is expanded through branch expansion rather than "encouragement" designs. Overall, the study suggests that expanding access to consumer credit can improve borrower outcomes, even at high interest rates, and provides valuable insights for policymakers and practitioners.