Pension plans of Buffett's Berkshire Hathaway Inc. earned 4 percent on their assets in 2005, ranking last among a group of 100 U.S. companies with the largest pension plans, according to Milliman, a Seattle-based benefits consulting firm. The average return was 11.3 percent.
Buffett, who has bet the U.S. trade deficit would weaken the dollar since 2002, may have made similar foreign-currency investments with Berkshire's pension assets, said Howard Silverblatt, an analyst at Standard & Poor's in New York.
"He took a beating on the dollar, so he might have taken a beating on this if he emulated that portfolio," Silverblatt said. Last year, Berkshire had $955 million in losses as the U.S. dollar index rose 13 percent.