us The largest public pension fund in the U.S. lost almost $67 billion in 12 months, more than 25 percent of its value, as stock markets tumbled.

The market value of the California Public Employees› Retirement System declined to $193.7 billion as of Oct. 9, from $260.6 billion a year earlier. Between Sept. 15, when Lehman Brothers Holdings Inc. filed for bankruptcy, and last week, the fund’s stock holdings declined by $12.4 billion to $36.8 billion, according to data compiled by Bloomberg.

Pensions and retirement accounts, which tend to be heavily invested in stocks, may have lost as much as $2 trillion since 2007, the Congressional Budget Office reported Oct. 7. In the 12 months through Friday, the Dow Jones Industrial Average dropped 40 percent, the Standard & Poor’s 500 Index, 42 percent.