The Illinois teachers' pension fund earned 19.6% on its investments to the end of June marking the highest return for the fund since the 1980s, thanks to significant growth from private equity and offshore investments.

The fund's 19.6% investment growth is in line with other large US pension funds over the period. The $247bn California Public Employees' Retirement System, the largest US pension fund, reported 19.1% growth on its portfolio over the same period with solid returns from international equities, and the $174bn California State Teachers' Retirement System posted a return of 21% on the back of high returns from real estate, international equities and alternative investments.