We use randomized interest rates, offered across eighty geographically distinct regions for twenty-nine months by Mexico’s largest microlender, to sketch the adjustment from a price change to a new equilibrium. Demand is elastic, and more so over the longer run; e.g. the dollars-borrowed elasticity increases from -1.1 in Year one to -2.9 in Year three. Credit bureau data do not show evidence of crowd-out, although this and other null results are imprecisely estimated. The lender’s profits increase, albeit noisily, starting in Year two. But competitors do not respond by reducing rates. These findings, together with other results, suggest that informational frictions are important, and that cutting rates furthered Compartamos Banco’s “double bottom line” of improving social welfare subject to a profitability constraint.

We document substantial cross-individual dispersion in U.S. credit card borrowing costs, even after controlling for borrower risk and card characteristics. That remaining dispersion arises because cross-lender pricing heterogeneity generates dispersion in annual percentage rate (APR) offers to borrowers, and borrowers vary in shopping intensity. Our empirics match administrative data to self-reported card shopping intensity and use instruments suggested by fair lending law to account for the endogeneity between APRs and search. The results show that shoppers versus nonshoppers pay APRs as different as those paid by borrowers in the best versus worst credit score deciles. We discuss implications for policy and practice.

We explore dynamics of limited attention in the $35 billion market for checking overdrafts, using survey content as shocks to the salience of overdraft fees. Conditional on selection into surveys, individuals who face overdraft-related questions are less likely to incur a fee in the survey month. Taking multiple overdraft surveys builds a “stock” of attention that reduces overdrafts for up to two years. The effects are significant among consumers with lower education and financial literacy. Individuals avoid overdrafts by making fewer low-balance debit transactions and cancelling automatic recurring withdrawals. The results raise new questions about consumer financial protection policy.

We posit that consumer lenders shroud interest rates and market “low monthly payments” to price discriminate on “fuzzy math” or “payment/interest bias”: consumers' pervasive tendency to underestimate borrowing costs when an interest rate is not disclosed. We test whether mandated disclosure changes lenders' ability to price discriminate using within-household interactions between payment/interest bias and policy-induced variation in the strength of Truth-in-Lending Act (TILA) enforcement across lenders and time. Weak TILA enforcement substantially widens the gap between rates paid by more-biased and less-biased borrowers. TILA compliance costs appear to increase interest rates overall, making the net effect on interest rates ambiguous.

Expanding access to commercial credit is a key ingredient of financial development strategies. There is less consensus on whether expanding access to consumer credit helps borrowers, particularly when loans are extended at high interest rates. Popular skepticism about “unproductive,” “usurious” lending is fueled by research highlighting behavioral biases that may induce overborrowing. We estimate the impacts of expanding access to consumer credit at a 200% annual percentage rate (APR) using a field experiment and follow-up data collection. The randomly assigned marginal loans produced significant net benefits for borrowers across a wide range of outcomes. There is also some evidence that the loans were profitable.

What Do Consumers Really Pay on Their Checking and Credit Card Accounts? Explicit, Implicit, and Avoidable Costs by Victor Stango and Jonathan Zinman. Published in volume 99, issue 2, pages 424-29 of American Economic Review, May 2009

Exponential growth bias is the pervasive tendency to linearize exponential functions when assessing them intuitively. We show that exponential growth bias can explain two stylized facts in household finance: the tendency to underestimate an interest rate given other loan terms, and the tendency to underestimate a future value given other investment terms. Bias matters empirically: More‐biased households borrow more, save less, favor shorter maturities, and use and benefit more from financial advice, conditional on a rich set of household characteristics. There is little evidence that our measure of exponential growth bias merely proxies for broader financial sophistication.

Policymakers often prescribe that microfinance institutions increase interest rates to eliminate their reliance on subsidies. This strategy makes sense if the poor are rate insensitive: then microlenders increase profitability (or achieve sustainability) without reducing the poor's access to credit. We test the assumption of price inelastic demand using randomized trials conducted by a consumer lender in South Africa. The demand curves are downward sloping, and steeper for price increases relative to the lender's standard rates. We also find that loan size is far more responsive to changes in loan maturity than to changes in interest rates, which is consistent with binding liquidity constraints.

It is often argued that people might take on too much high-cost debt because they are present focused and/or over-optimistic about how soon they will repay. We measure borrowers’ present focus and over-optimism using an experiment with a large payday lender. Although the most inexperienced quartile of borrowers under-estimate their likelihood of future borrowing, the more experienced three quartiles predict correctly on average. This finding contrasts sharply with priors we elicited from 103 payday lending and behavioural economics experts, who believed that the average borrower would be highly overoptimistic about getting out of debt. Borrowers are willing to pay a significant premium for an experimental incentive to avoid future borrowing, which we show implies that they perceive themselves to be time inconsistent. We use borrowers’ predicted behaviour and valuation of the experimental incentive to estimate a model of present focus and naivete. We then use the model to study common payday lending regulations. In our model, banning payday loans reduces welfare relative to existing regulation, while limits on repeat borrowing might increase welfare by inducing faster repayment that is more consistent with long-run preferences.