Ben S. Bernanke, the world’s most-powerful central banker, says he doesn’t understand gold prices. If his peers had paid attention, they might have stopped expanding reserves that lost $545 billion in value since bullion peaked in 2011.

Bernanke, who holds economics degrees from Harvard College and the Massachusetts Institute of Technology and led the Federal Reserve through the biggest financial disaster since the Great Depression, told the Senate Banking Committee in July that “nobody really understands gold prices and I don’t pretend to really understand them either.”

Central banks, which own 18 percent of all the gold ever mined, will add as much as 350 tons valued at about $15 billion this year, the London-based World Gold Council estimates. They purchased 535 tons in 2012, the most since 1964. Russia is the biggest buyer, expanding reserves by 20 percent since prices reached a record $1,921.15 an ounce in September 2011. Gold slumped 31 percent since then.

As policy makers were buying, investors were losing faith in the metal as a store of value. The value of exchange-traded products dropped by $60.4 billion, or 43 percent, this year, saddling hedge fund manager John Paulson with losses, according to data compiled by Bloomberg. Billionaire investor George Soros sold his holdings in the biggest gold-backed ETP this year and mining companies wrote down the values of their assets by at least $26 billion.