The proliferation of low-cost index funds that track various asset classes makes the implementation of this strategy easy.

FORBES: How to Pick Asset Classes

Some vigorous critics of 401(k) plans have argued that the plans will get better soon, thanks to the proliferation of low-cost exchange-traded index funds and new rules that force the plans to more fully disclose their costs to investors.

FORBES: How To Fix Your Lousy 401(k) Retirement Plan: Pool It, Like a Pension Fund