Given mutual fund popularity, we thought it would be bigger. Granted, 22 percent of any market is nothing to sneeze at. According to ICI, at year-end 2008 mutual funds accounted for $3.1 trillion, or 22 percent, of the $14 trillion U.S. retirement market. The remaining $10.8 trillion of year-end 2008 retirement market assets were managed by pension funds, insurance companies, banks, and brokerage firms.