Not all replacement rate studies are the same, according to David Blanchett, research consultant from Morningstar's Investment Management division. And that could seriously hurt your clients.

Blanchett recently completed a research paper about the level of inaccuracy in the replacement rate studies that plan sponsors and consultants frequently request and undertake.

"Well-minded defined contribution plan fiduciaries and their consultants are increasingly interested in making sure their plan participants are 'on track' for a successful retirement," he writes. "We certainly applaud this mindset and the pursuit of the adoption of plan policies, investments and investment programs that will lead to a successful retirement. The pursuit of this goal naturally leads plan sponsors to focus on a variety of measures that assist the plan sponsor in determining if their participants are on track."