Excerpt: [O]ne problem with the current system has gotten little attention: Using investment fees to pay for other aspects of 401(k) expenses means investors in some high-cost funds, like actively managed funds, pay a much greater share of a retirement plan's fixed costs than investors in more basic options like company stock or an index fund. 'The concern is it's not equitable,' says Lori Lucas, leader of consulting firm Callan Associates Inc.'s defined-contribution practice. 'Some people could pay almost all of the costs. Some could pay none of the costs. What funds you select can determine whether you pay or not.' A recent Callan study found that only one in eight plans that used revenue sharing actually had their entire menu of funds contributing to the plan's upkeep. In about a third of plans, half the funds or fewer contributed.  MORE >>