You should be able to get return information from State Pension Funds that invest in private equity/venture capital.
For example, the Washington State Investment Board Private Equity IRR report can be access at http://www.sib.wa.gov/financial/invrep_ir.asp. From December 2013 IRR Report [PDF] at http://www.sib.wa.gov/financial/pdfs/quarterly/ir123113.pdf,
U.S. Venture Partners VIII, L.P. 6/4/2001 3.23%
New Enterprise Associates 10, L.P. 10/17/2000 3.16%
Menlo Ventures X, L.P. 1/6/2006 0.66%