Of employers responding to a 2009 Hewitt survey, 69% said they're very or somewhat concerned about plan expenses, up from 61% who said that in 2007.
Of companies, 84% said they've attempted to calculate the total cost of maintaining their 401(k), up from 60% in 2007 and a measly 29% in 2001, according to the survey.
The No. 1 reason companies cite for having not calculated the total cost? Complexity.
For participants invested in mutual funds, the fund expense ratio is often the sole fee, and it's detailed on the fund fact sheet, Hewitt's Hess said.
But that doesn't tell the whole story. "You have to disclose the expense ratio but you don't have to disclose revenue sharing, which is how those administrative fees are paid," Hess said.
Particularly in smaller plans, participants may find extra costs, Hess said, or a flat fee every year.
"A friend at a smaller plan had 90 basis points added to every fund fee," she said. At other plans, "you have to pay $75 every year to be in your 401(k) but you get to use all these separate accounts" that have really low fees.
"There are a million different ways to do it. There's no right or wrong way and it's very hard to compare," she said.
Fees are one way plans differ widely. Investment options are another.
Some of the investments offered "might be all passive, some might be active and passive, some might have five funds, some might have 55 funds," Hess said. "There is quite a lot of variation. Not to say they're right or wrong, just different."