Over 30 percent of the world's adults lack access to basic financial tools---more often women, members of minority groups, and poor families. The abilities to buy what you need, when you need it, to put money aside for the future, and to withstand bad luck without financial ruin seem like basic elements of life in a functioning economy. But life is not that simple for people who lack financial tools. In fact, the tighter the budget, the more you need...