CalPERS warns about stock

The California Public Employees’ Retirement System, the largest U.S. public pension fund, may have to seek bigger contributions from employers than it forecast a month ago.

CalPERS is sending letters this week warning local governments in the state that if stock market losses are sustained, their contributions for employees’ retirement benefits may rise more than estimated in October for the year starting in July 2010. Last month, the fund said it might impose an increase of as much as 4% for that year if returns fell 20%.