The hedge-fund billionaire and a global advocate has transferred $18 billionin assets to his long-time philanthropy.

With the gift, to be distributed over several years, the foundation becomes the second largest U.S. philanthropy, behind the Bill & Melinda Gates Foundation. Open Society already spends close to $1 billion a year to promote democracy and human rights in more than 120 countries.

Among its investments: the first fund of Leapfrog Investments, the frontier-market financial-services investor that has raised more than $1 billion across multiple funds; Aspada Investments, an Indian early-stage venture capital firm that focuses healthcare, education, agriculture and financial services; and Media Development Investment Fund, which invests in independent media in countries often hostile to a free press.

This article on impact philanthropy was written by Dennis Price at ImpactAlpha