13 March 2026

The Problem Of 401(k) Mapping To ‘Dominated’ Funds

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Ian Ayres, Forbes:

In a working paper that was just accepted for publication in the Yale Law Journal (coauthored with Quinn Curtis) and in a recent Freakonomics blog post, I document the problem of “dominated funds[.]”

Retirement regulations have largely been successful in giving worker/participant defined contribution plans the opportunity to diversify. Most plans nowadays give participants a sufficient variety of investment options that it is possible to allocate investments so as to diversify away most idiosyncratic risks.

However, the 1974 Employment Retirement Income Security Act’s (ERISA) emphasis on diversification has diverted attention from the problem of excess costs. Courts evaluating whether plan fiduciaries have acted prudently have tended to just ask whether the plan offered a sufficient number of reasonably-priced investment opportunities. For example, in Hecker vs. Deer & Co. (7th Cir. 2009), the 7th Circuit found it was “untenable to suggest that all of the more than 2500 publicly available investment options had excessive expense ratios.”

The Hecker approach is wrongly decided because it effectively immunizes fiduciaries that offer what Quinn Curits and I call “dominated funds” in their fund menus.

A dominated fund is a fund that no reasonable investor would invest in given that plan’s other investment offerings. In our recent working paper, we find that:

[A]pproximately 52% of plans have menus offering at least one dominated fund. In the plans that offer dominated funds, dominated funds hold 11.5% of plan assets and these dominated investments tend to be outperformed annually by their low-cost menu alternatives by more than 60 basis points.

Informed investors should be investing 0.0 percent of their plan assets in dominated funds, so it’s disturbing to see that when given the opportunity, 11.5 percent of plan assets flow into these funds.

To my mind, dominated funds are a kind of product design defect:

A car or computer manufacturer which included a button on their product which had no beneficial purpose and would only cause the device to perform less safely would run a substantial risk of being held accountable under product liability for failing “to design a product to prevent a foreseeable misuse.” The fact that informed consumers would not push the button would not absolve the manufacturer from including an option that no reasonable user should ever push if it was foreseeable that even some users would misuse the product by pressing the button. The likelihood of investor misallocation is just as foreseeable.

I’ve argued that the problem of dominated funds suggests a simple reform:

Plan fiduciaries should have a duty to remove dominated funds from their menu and to map participants to the lower-cost analog offering (akin to 404(c)(4) “Like-to-Like” mapping procedure).

But a recent decision suggests the possibility of an even more pernicious problem. Instead of failing to map participants’ investments away from dominated funds, Tussey vs. ABB, Inc. suggests the possibility that fiduciaries at times might be eliminating funds and mapping these investments toward high-cost dominated funds. In the Tussey case, the retirement plan at issue eliminated from its menu of funds the Vanguard Wellington fund and “mapped” all investments in that fund to Fidelity Freedom funds.

Mapping is the default allocation that fiduciaries use when they eliminate a fund from their menu offerings. Participants who are invested in the eliminated fund are reinvested in the mapped fund if they do not affirmatively select an alternative menu fund that is still be offered. Many, many employees don’t pay attention to plan notices that a fund is being eliminated and are mapped to the default investment, so the mapping allocation often determines where the bulk of the eliminated fund investments will be reinvested.

Click here for the full column.

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