Employer-sponsored retirement assets hit $10.9 trillion

The survey adds that 401(k) plans are the most widely adopted plan in the private sector. Most plans have fewer than 50 participants, but assets and participating employees are concentrated in plans with 1,000 or more participants.

The report adds that 401(k) plan assets have grown at an annual average rate of 3.4 percent over the past five years, attaining $3 trillion in 2012, up from $2.7 trillion in 2011.

Participants' investment allocations are more equity-oriented now than at the height of the economic crisis of 2008. In 2012, equity allocations — including diversified equity, company stock and balanced/asset allocation funds — garnered in the aggregate for 69 percent of investors' portfolios, as compared to 56 percent in 2008. However, the 2012 total remains below the 2006 peak of 74 percent for these funds in 2006.

The survey notes also that more than 80 percent of IRA assets are held in mutual funds or self-directed brokerage accounts, accounting for $2.4 trillion and $2.1 trillion, respectively, of the $5.4 trillion total. Additional IRA assets are held by life insurers ($451 billion) and banks, credit unions and savings institutions ($487 billion), the report states.