Not all of the data is private...
The vast majority of performance information on venture capital and private equity funds is kept under wraps, even by many public pension systems and state university endowments. But several of these groups, thanks to local law, do make the information publicly available. Sometimes via their websites, or sometimes via special request.
Each report differs in terms of specific funds, types of information disclosed and time period. What follows is data from some of the larger systems that publicly report (one exclusion here is CalPERS — due to difficulties in downloading the data, but you can view their information by going here).
University of Texas Investment Management Company (UTIMCO)
Massachusetts Pension Reserves Investment Management Board
Oregon Public Employees Retirement Fund
University of California Regents
California State Teachers’ Retirement System (CalSTRS)
Washington State Investment Board