from The New York Times:
… I came to think of impact investing as a private equity fund for social change. This may sound like an oxymoron, given the criticism that private equity funds have faced recently over their management of companies they have taken private. But the structure is similar: there are three or four capital calls in the first year, and the fund is not fully invested until the fourth year. As the end of its investment period nears, the fund then starts to look for ways to sell its investments. Doing good matters to investors, but they also hope for private equitylike returns of close to 20 percent a year.
… The Global Impact Investing Network, a nonprofit group, said that current impact investments amounted to about $50 billion. It projects this area to grow to $500 billion by 2014, putting it at roughly 1 percent of all managed assets.