Retirement assets in the U.S. hit a record $17.8 trillion as of the end of the third quarter 2007, according to the latest quarterly figures from the Investment Company Institute, the mutual funds industry trade group.

Individual retirement accounts comprised the largest portion U.S. retirement assets at $4.8 trillion,or nearly 27%. The rest of the assets came from defined contribution plans at $4.5 trillion and government pension plans at $4.4 trillion (both about 25%), private defined benefit plans (14%), and annuities (9%).