Higher management costs do far more to erode a typical American's long-term savings than does the high-speed trading highlighted in Michael Lewis' new book, "Flash Boys." Kinnel said computerized trades operating in milliseconds might cost a mutual fund 0.01 percent during the course of a year, a microscopic difference compared with yearly fees.
"Any effort to shine more light (on fees) and illustrating that impact is huge," Kinnel said. "Where we've fallen down most is not providing greater guidance for investors in selecting funds."
The Investment Company Institute, a trade group, said 401(k) fees for stock funds averaged 0.63 percent in 2012 (lower than the 1 percent average figure the Center for American Progress uses), down from 0.83 percent a decade earlier. The costs fell as more investors shifted into lower-cost index funds. They've also declined because funds that manage increasing sums of money have benefited from economies of scale.
"Information that helps people make decisions is useful," said Sean Collins, the institute's senior director of industry and financial analysis. "Generally, people pay attention to cost. That shows up as investors tend to choose — including in 401k funds — investments that are in lower than average cost funds."
But many savers ignore fees.
In a 2009 experiment, researchers at Yale and Harvard found that even well-educated savers "overwhelmingly fail to minimize fees. Instead, they placed heavy weight on irrelevant attributes such as funds' (historical) annualized returns."
The Labor Department announced plans last month to update a 2012 rule for companies to disclose the fees charged to their 401(k) plans. Fee disclosures resulting from the 2012 rule proved tedious and confusing, said Phyllis Borzi, assistant secretary for the Labor Department's Employee Benefits Security Administration.
"Some are filled with legalese, some have information that's split between multiple documents," Borzi said.
Americans hold $4.2 trillion in 401(k) plans, according to the Investment Company Institute. An additional $6.5 trillion is in Individual Retirement Accounts.