Total U.S. retirement assets climbed 3.9 percent to a record $21.7 trillion in the third quarter, the Investment Company Institute said.

The assets include those in IRAs, defined contribution and defined benefit plans, government plans and annuity reserves. Retirement assets accounted for 34 percent of all household assets, unchanged from the previous quarter.

At the end of September, IRAs held $6 trillion, up 4.6 percent for the quarter. Defined contribution plan assets rose 4.4 percent to $4 trillion. Assets held by federal, state and local government pension plans were $5.4 trillion, a 3.7 percent increase.

Private defined benefits plan assets were $2.9 trillion at the end of the quarter and annuity reserves were pegged at $1.9 trillion.

The bulk of 401(k) money, 59 percent, was invested in mutual funds. For IRAs, the figure was 46 percent.

The amount of retirement assets invested in target date mutual funds was $573 billion, a 6.1 percent increase. The institute said 89 percent of target date mutual funds were held in retirement accounts.

In October, the institute reported that IRAs held a lower percentage of equities than they did before the recession.