Employees are once again ramping up their commitment to their 401(k) plans.

Just 2.4 percent of Defined Contribution plan participants stopped contributing in 2010, compared with 3.4 percent of participants in 2009, according to the ICI's latest quarterly study.

At the same time, DC plan withdrawal activity in 2010 was in line with the prior year's activity; participants generally did not tap their accounts. Only 3.5 percent of DC plan participants took withdrawals during 2010, with only 1.7 percent taking hardship withdrawals-similar to the 3.1 percent and 1.6 percent levels seen in 2009.

The study is based on recordkeeper data from more than 23 million DC plan participant accounts.

Last month, the ICI reported that total US retirement assets were $17.5 trillion at year-end. This worked out to a 5.2 percent increase in the fourth quarter of 2010 and 9.1 percent for the year.

Retirement savings accounted for 37 percent of all household financial assets in the United States at year-end 2010.

One source of concern: Loan activity edged up throughout 2010. It found 18.2 percent of DC plan participants had loans outstanding at year-end 2010, compared with 16.5 percent at year-end 2009. This is money that suddenly is not generating gains, which could have been substantial given the stock market's near doubling since the March 2009 low.

In general, it is not in the best interests of employers to have employees who are knee deep in all kinds of debt. They are more likely to be distracted or prone to taking outsized risks.