The merits of investing in private versus public equity have generated considerable debate, often fueled by concerns about data quality. In this paper, we use cash flow data derived from the holdings of almost 300 institutional investors to study over 1,800 North American buyout and venture capital funds. Average buyout fund returns for all vintage years but one before 2006 have exceeded those from public markets; averaging about 3% to 4% annually. Post-2005 vintage year returns have been roughly equal to those of public markets. We find similar performance results for a sample of almost 300 European buyout funds. Venture capital performance has varied substantially over time. North American venture funds from the 1990s substantially outperformed public equities; those from the early 2000s have underperformed; and recent vintage years have seen a modest rebound. The variation in venture performance is significantly linked to capital flows: performance is lower for funds started when there are large aggregate inflows of capital to the sector. We also examine the variation in performance of funds started in the same year. We find marked differences between venture and buyout leading to a much more pronounced impact of accessing high performing funds in venture investing.