Defined contribution assets came next, totaling $6.8 trillion, and up by 2.1 percent in the quarter.

After that were assets in government defined benefit plans, totaling $5.2 trillion and up 1.9 percent for the quarter; that includes federal, state and local government plans.

Private-sector defined benefit plans trailed with $3.2 trillion in assets, up only marginally at 1.01 percent for the quarter, while annuity reserves outside of retirement accounts accounted for another $2 trillion, up 1.02 percent.

Among employer-based DC plans, $4.6 trillion of the total was held in 401(k) plans at the end of the year. For other types of plans, $560 billion was in private-sector DC plans; 403(b) plans held $951 billion; 457 plans accounted for $261 billion; and the Federal Employees Retirement System’s Thrift Savings Plan held $427 billion.

Of all DC plan assets, mutual funds managed 55 percent, totaling $3.7 trillion. In addition, 48 percent of IRA assets — $3.5 trillion — were held in mutual funds.

ICI also said that unfunded liabilities for total retirement assets in the U.S. amounted to $3.1 trillion, with government DB plans liable for more of the total than private DB plans.

As of the end of 2014, it said, unfunded liabilities made up 1 percent of private-sector DB plan entitlements, 25 percent of state and local government DB plan entitlements, and 56 percent of federal DB plan entitlements.

Total U.S. retirement entitlements included not just the $3.1 trillion in unfunded liabilities but also $24.7 trillion in retirement assets. Taken together, both the funded and unfunded retirement entitlements made up 41 percent of the financial assets of all U.S. households as of the end of December.