Investors pulled a net $3.79 billion from stock mutual funds in May as the market rose. It was the second straight month of outflow, and it was more than double April’s outflow of $1.56 billion, according to the Investment Company Institute. And signs point to even larger outflow this month. Stock mutual funds that invest primarily in the U.S. disgorged $16.69 billion in new money in May vs. outflow of $19.77 billion in April.