"Academics have been trying to work out from the evidence whether microcredit does actually raise people's incomes.
But it's been hard to do a proper scientific survey, since you need to compare those who do get a loan with a control group of similar people who don't.
Dean Karlan, professor of economics at Yale University, has managed to do it - with a control group - in the Philippines. His results raise some serious questions about the effectiveness of microcredit in reducing poverty."
I definitely recommend listening to the interview with Karlan.