There is no concrete evidence for the same. However, there could be scenarios where this was true. The pensions require higher returns since people are living longer. Thus, following the safe and traditional bond route will not suffice. Thus, the partnership between pension funds and private equity funds could work well for the following reasons-

Any investment decision, big or small, will begin and end with a simple question: How much do I stand to make? Since there financial crisis of 2008-09, top-tiered private equity funds have started outpacing equity returns significantly.

Another advantage that private equity funds have overstock markets is the low tendency for daily volatility. Funds typically invest over ten-year horizons, while valuations are infrequent and rarely revealed. Additionally, the complexity of the funds makes it difficult for investors to react to their decisions exuberantly. 

The private equity market is especially suited to the goals and investment profile of pension funds.