Mutual fund families, despite serving as retirement plan fiduciaries and hosting "open architecture" plans, nevertheless favor their own fund offerings, according to new research.

In an academic paper published late last month, Veronika Krepely Pool and Irina Stefanescu, both of Indiana University, and Clemens Sialm of the University of Texas at Austin say that poorly performing funds are more likely to appear on 401(k) menus if they are affiliated with the plan trustee.

Titled It Pays to Set the Menu: Mutual Fund Investment Options in 401(k) Plans, the study eliminates the possibility that trustees maintained a proprietary fund on the plan menu because of information that the fund was poised to outperform, since subsequent performance was disappointing.