Mutual funds experienced net inflows of $27 billion in May, according to estimates released last week by Lipper. All three major fund categories experienced inflows. Equity funds had net flows of $10.2 billion, fixed income funds had flows of $9.8 billion and money market funds had flows of $7 billion.

"This market has been as frustrating to investors as a tire's slow leak. They keep adding money but don't see any sustained gains," said Don Cassidy, a senior research analyst at Lipper. "Still, to say that all investors are discouraged or scared is an oversimplification."

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