ImpactAssets has released its fourth annual online guide highlighting fund managers that deliver social or environmental impact benefits in addition to financial returns.

The list, called IA 50, focuses on fund managers in the United States, Africa, Europe and Latin America that manage a combined $15.5 billion in assets.

To be considered for the IA 50, fund managers need to have at least $10 million in assets under management, more than three years of experience with impact investing, and have made a measurable positive impact, according to ImpactAssets.

Examples of funds highlighted for 2014 include:

• Portland, Ore.-based Ecotrust Forest Management (EFM), a private forestland investment management organization that practices ecological forestry, focusing on improving forest health and productivity while producing high-quality logs, ecosystem services such as carbon offsets and jobs for local communities.

• The Media Development Investment Fund, which provides affordable financing and technical assistance to independent news businesses in countries with a history of media oppression.

• The UNICEF Bridge Fund, which is a financial tool created by the U.S. Fund for UNICEF to speed up lifesaving assistance to children in need around the globe. It provides capital to bridge timing gaps between donor commitments to UNICEF and the actual receipt of cash. This allows for a continuous supply of health and educational products from reliable manufacturers to vulnerable children worldwide.

"The IA 50 is a solid starting point for investors and advisors looking for fund managers with established track records across a range of impact investment criteria," said Matthew Weatherley-White, managing director of The Caprock Group. "Investors who have been watching from the sidelines and waiting for the field to mature will find no shortage of opportunities."

ImpactAssets is a nonprofit financial services firm that advances social or environmental change through investment. The IA 50 list can be viewed here.