When the Afghan government used mobile phones instead of cash to pay some of its policemen, the officers thought they'd just had a 30 percent pay rise. In truth, they had just been paid the full amount, with nothing skimmed off by middlemen, for the first time.

This anecdote from the U.S. Agency for International Development shows how technological innovations such as mobile banking and biometrics have helped integrate more people in emerging markets into the formal financial system, opening up opportunities for banks willing to take a chance.