After decades on the fringes, impact investing is going mainstream. Though the phrase isn't yet commonplace, the concept is familiar enough to have spawned several monikers: values-based investing, green investing, mission-driven investing, sustainable investing, socially responsible investing, principled investing. Some 3,000 investors and entrepreneurs convened at Fort Mason this week to discuss the idea at SOCAP, the leading conference for people who want to support social innovation with their money. "Social-impact investors want to make sure they are doing good in the world but as a genuine investment, not philanthropy," said Eryc Branham, CEO of MissionHub, which produces the conference. The rapidly growing field measures returns not just in dollars and cents but in social and environmental change. On the financial side, some investors accept lower returns as a trade-off for doing good. But they don't necessarily have to. A new report from the Wharton School at the University of Pennsylvania found that pursuing a social agenda doesn't come at a financial price. After studying 53 funds with 557 investments, Wharton found that their rate of return from 2000 to 2014 was in line with benchmarks like the Standard & Poor's 500 index. While impact investing amounts are still small compared with the multitrillion-dollar financial market, the potential for making a difference is immense.