The average expense ratio 401(k) investors paid for owning stock mutual funds declined ever so slightly in 2010, according to a release by the Investment Company Institute.

The fee dropped from .74 percent in 2009 to .71 percent in 2010. But it was .72 percent in 2008, making you wonder if the ever present spotlight on retirement plan fees is really doing much.

Expense ratios on bond funds held steady at .56 percent. Money market funds saw a big decrease in fees paid - from .37 percent in 2009 to .28 percent last year. That isn't surprising, considering that in 2010, money market mutual funds had a hard time earning enough to stay in positive territory once fees were paid.

According to the report, investors tend to select funds with lower fees and stick with those funds over time. They also shy away from mutual funds with loads, or sales charges.

401(k) fees have come under scrutiny in recent years, with critics arguing that the main retirement vehicle for many Americans is riddled with confusing or hidden fees. In January, the Government Accountability Office reported that the sponsors of 401(k) plans have conflicts of interests because of revenue-sharing and other undisclosed financial arrangements.

A company called BrightScope has tried to shed light on the costs of participating in a 401(k) plan, with ratings and reports about most sizable companies. You can check out BrightScope's data on your company 401(k) at www.brightscope.com.