A key barometer of the health of the private equity sector has revealed that funds gained 15% overall last year, with those invested in distressed and mezzanine debt posting the largest advances.

The State Street Private Equity Index, which compiles returns for 1,717 funds, also revealed that the aggregate internal rate of return for these funds was 5.94% in the fourth quarter. This was the third consecutive quarter with positive returns above 5% after five straight quarters of negative returns.