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Do Mutual Funds Manipulate Star Ratings? Evidence from Portfolio Pumping

This paper reveals that mutual fund managers manipulate Morningstar star ratings by inflating their month-end portfolio values when they are likely to finish the month near rating cutoffs. This star rating manipulation is more pronounced among funds with greater incentives and abilities to pump their portfolios and manipulate star ratings. Following heightened regulatory scrutiny, portfolio pumping to manipulate star ratings has largely migrated from quarter/year-ends to less prominent month-ends. Improving star ratings, portfolio pumping increases fund flows, especially in the month of a rating upgrade. Placebo tests exploiting the June 2002 change in Morningstar rating methodology yield expected null effects.