With government resources and charitable donations insufficient to address the world’s social problems, impact investing offers a new alternative for channelling large-scale private capital for social benefit, emerging as an alternative asset class, with a wide variety of investors across regions and business sectors. Across selected businesses in five sectors the market potential over the next 10 years is $400 billion - $1 trillion for invested capital and profit of $183 - $667 billion. Measuring and monitoring social performance is essential but challenging and potentially expensive. Market initiatives are in place to build third-party systems to facilitate these efforts.