The investors are mostly institutional investors, including banks, governments, public and private pension funds, endowments and foundations. Public and private pension funds, endowments and foundations account for 70 percent of the funds invested with the top 100 PE firms since 2005, according to Preqin.

The 20 largest U.S public pension funds for which data is available (including the California Public Employees Retirement System, the California State Teachers Retirement System, the New York State Common Retirement Fund, and the Florida State Board of Administration) have invested nearly US 140 billion on behalf of their nearly USD 10 million beneficiaries.