PEOPLE stream in as the doors to a massive stone building open. Guards in khaki uniforms wield ancient British rifles as men in crisp white dhotis and women in colourful saris direct the flow of customers toward the 14,000 people who work here, at the Mumbai branch of the State Bank of India. Gold-buyers go to the left where they are offered certified coins or ingots that come in sealed plastic cases. A dozen naval officers wait patiently: their salaries, like those of many state employees, are paid through the bank. At a counter upstairs, tellers help illiterate Nepalese migrant workers to send money home.

That is one way to provide financial services: have a bank do it. Defenders of this approach say that it brings the unbanked into the financial mainstream by getting them accustomed to using banks rather than informal services. But it is both expensive—bank branches cost a lot to build and staff—and inefficient. In India only a rich minority of citizens have bank accounts, and two-thirds of adults—many of them rural and poor—have no access to financial services at all. Why should they have to spend time, effort and money to travel to a bank branch?