Treasuries are getting an unexpected boost from pension funds controlling more than $14 trillion.

Fund managers for companies including General Motors Corp. and Alcatel-Lucent are shifting away from stocks to prepare for accounting changes requiring them to more fully disclose the value of their holdings. Bonds are gaining favor as funds seek to avoid wider swings in prices that may accompany equities as the new rules take effect, possibly later this year.

The switch couldn’t come at a better time for the $4.4 trillion market for American government bonds, which hasn’t returned more than 3.5% a year since 2002. The surge in equities this month to record highs has wiped out the pension deficits of the companies in the Standard & Poor’s 500 for the first time in six years, according UBS Securities LLC. Now the funds can afford to match future obligations to employees with fixed-income securities rather than trying to plug shortfalls in the funds.

“You put all that together, and you say, hey, at the end of the day we really don’t need the volatility” of stocks, a chief executive and investment officer at General Motors Asset Management Corp. in New York, Nancy Everett, said. The fund is shifting 20% of the largest American automaker’s pension assets into bonds from equities.

Demand from pension funds is typically strongest for the longest-maturity debt, which allows funds to more closely match assets with liabilities.