As the DOL's fee disclosure regulations take effect early this year, it's becoming increasingly important that 401(k) managers understand where their fees rank and if they're reasonable.

 With this in mind, the 12th edition of the 401k Averages Book released the average total plan costs for a small retirement plan (100 participants), which, in 2011, for all expenses bundled together was 1.3 percent of assets under management. For a large retirement plan (1,000 participants), the number was slightly lower at 1.08 percent.

The annual benchmarking report shows that small plan average investment fund expenses borne by participants was 1.24 percent of assets, while for large plans, average investment fund expenses were 1.05 percent. Investment expenses accounted for 95 percent of the small plan's total expenses and 98 percent of the large plan's expenses.