However, looking at individual funds, only a few have delivered above average performance over one and five years.
And then there are people who work at hedge funds.
The study also looked at domestic funds but found the performance gap to be far smaller.
People think they can make money fast at hedge funds.
Independent directors at large mutual funds can earn more than $100,000 a year.
The study looked only at mutual funds, which are required to report their holdings and performance regularly.
At large funds, this means that a single year's winnings can set up the managers for life.
"People at hedge funds don't tend to interact with one another."
His investigation has focused on two types of trading at mutual funds.
If you look at actively managed funds alone, he said, Fidelity is more competitive.
