The purpose of this paper is to examine market concentration, economies of scale, economies of scope, and the relative size of a particular fund, within a fund family, as determinants of mutual‐fund expense ratio. This examination is focused at the asset‐manager level and is based on the Morningstar equity and fixed‐income style classifications.
All data used in this study come from the July Morningstar Principia database for the years 1997 through 2006. One challenge of working with these data is that Morningstar treats each separate class of a fund as though it were an individual fund. As a result all Morningstar data items are reported for each fund class as though they are data items for a separate fund. The data are modified so that the items for separate classes of a fund are merged into data for a single fund. For example, assets in a fund become the total of the assets in each class of the fund.
This study contributes to the literature on mutual‐fund managers, and the literature on the structure of mutual funds, by showing that market concentration at the asset‐manager level varies substantially across Morningstar styles, particularly for the fixed‐income funds. The paper shows that increased market concentration is associated with greater expenses for the funds under management, within a given Morningstar‐style box, for both equity funds and for fixed‐income funds. We also show that increased costs are partially offset by economies of scope for the fixed‐income funds.
This paper extends the current literature in several ways. First, it confirms the existence of economies of scale at the fund level within Morningstar style classifications. Second, it documents the existence of varying levels of market concentration within different Morningstar style classifications. Third, the results demonstrate that there is a negative relation between the scope of funds handled across the Morningstar classifications by a particular fund manager and the expense ratio for particular funds. Finally, the results presented in this paper show that the largest funds within a family are associated with the highest expense ratios in the family.
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