Not a quant question, but not suited for Money stack exchange... I've heard rumblings of a trend of pension funds co-investing with private equity and was curious as to the reasoning of that strategy and if there really is a known trend.
I would venture a guess that the pension plans seek similar long-term horizons to private equity and that makes them natural partners and the benefit to the pension plan would simply be to not have to invest the entire amount of capital required for the deal.