"As of September 30, retirement assets were up 3.5% from the $18.7 trillion recorded on June 30. ICI reports that the increase in retirement assets can be attributed to the rise in corporate equity values -- the S&P 500 total return index grew by 6.4% in the third quarter. At the end of the third quarter, retirement savings made up 36% of all household financial assets. Individual retirement accounts (IRAs) swelled 4.3% since the end of the second quarter to reach $5.3 trillion, 46% ($2.4 trillion) of which was invested in mutual funds."