Retirement Clearinghouse has been working to provide portability options for 401(k) assets left behind when employees change jobs.

Although rolling assets into a new plan isn't necessarily seen as complex, workers do see it as time-consuming, estimating that it would take them a median of 9 hours to complete, and as a "mystery" that they'd need to have explained to them.

The study also found that employees aren't necessarily eager to cash out those plans. Only 4 percent of those who cashed out in the past two years said they would intend to cash out if they left their current plans, and half of those who did cash out of a plan said they wouldn't have done it if rolling in were made as easy as cashing out.

Most who cashed out also agreed that defined contribution balances should only be used for retirement, and half of those who cashed out still regret doing so.

Of those who rolled into a new employer's plan, two thirds said the process "requir[ed] some work," and that on average it took 3-4 weeks. In addition, two thirds of those who actually completed the roll-in process asked for help from other people to get through it — and two thirds of those had that other person handle the whole roll-in process.

Consequences of not rolling over

Among those who just left assets stranded at a previous employer, 20 percent said "it wasn't big enough to bother"; 17 percent said "it seemed to be very hard to do"; 17 percent said "I didn't have the time"; and 22 percent said "I was not sure how to do it."

When made aware of how much they'd have at age 65 if they didn't cash out, a third said they'd rethink the decision to cash out, and nearly half of participants say that, compared with existing employee benefits, roll-in assistance would be an "excellent" employee offering. Nearly that many said it would be a "good" benefit.

The study suggests that plan sponsors "should clearly specify the consequences of cashing out" in a way that overcomes employees' tendency to discount what they are losing by doing so.

Specifically, sponsors should reframe the cost in terms of loss of asset accumulation from the day they cash out until retirement, and also in terms of loss of monthly retirement income.

Sponsors should also make the penalties for cashing out greater, and make roll-ins "substantially" simplified, as well as offering roll-in assistance as an employee benefit.