Is the South African government right to think that credit has gone too far? Rather than relying on theology or theory to answer this question, a recent working paper offers some rare evidence. Dean Karlan, a Yale economist who is co-director of the Financial Access Initiative, and Jonathan Zinman, of Dartmouth College, studied a profit-seeking lender that served some of South Africa's poorer neighbourhoods. Suspecting that its credit standards were too strict, the lender was willing to experiment with a looser provision of credit. It asked its loan officers in Cape Town, Port Elizabeth and Durban to reconsider 325 out of 787 applicants who had narrowly missed out on approval for a loan. The lucky 325 were chosen at random—nothing distinguished them from the remaining 462, except the luck of the draw. This allowed the researchers to establish a causal link between the loan and changes in the lives of the applicants.

Most of the new customers took a four-month loan at an annual interest rate of about 200%: a 1,000-rand loan, for example, would be repaid in four monthly instalments of 367.50 rand. For the bank, the study proved the wisdom of stretching its lending limits. The new clients were profitable, if not as profitable as the borrowers already on their books. The authors reckon the bank made a gain of at least 201 rand per loan.

Did these profits come at the expense of the poor? On the contrary. Despite the demanding terms on offer, those reconsidered for a loan seemed to prosper. Six to twelve months later, they were less likely to go hungry, and their chances of being in poverty fell by 19%. Not coincidentally, they were also more likely to have kept their jobs, perhaps because the credit helped them to overcome emergencies that might otherwise have forced them to abandon their posts. About a fifth of them, for example, spent their loan on transport, such as buying or repairing a car that they might have needed to get to work.