Pension funds have traditionally invested very small parts of their portfolios in riskier investments. It's usually done to slightly enhance yield.

But in the past decade pension funds have increased their "alternative" investments since their traditional bread and butter,bonds and fixed income, have had abysmal yields due to low interest rates. Yet with pension payout obligations having only gotten bigger (especially in europe, with the aging population, the pressure to generate returns is pushing the fund managers to seek out riskier and riskier investments.