In April, Mexico's Banco Compartamos went public, raising $450 million. By the end of the first day's trading, the bank was worth more than $1.8 billion, and the people who had invested money in the bank during its early days found themselves sitting on enormous profits. It was a glorious day for Mexcian capitalism – except for one small problem: Banco Compartamos is a microfinance institution, devoted to improving the lives of the poor. What was it doing, then, improving the lives of already-rich private shareholders instead?

Development group CGAP was one of the early supporters of Compartamos, although it gave grants rather than equity capital, so it made no profit on the IPO. The group has now released a comprehensive report by Richard Rosenberg about what happened, and whether the outsize IPO profits came at the expense of the poor people Compartamos was founded to serve. In a word, it seems, the answer is yes.