Even though Congress ordered the General Accounting Office (GAO) to look into high mutual fund fees and profits, no one yet can say exactly how lucrative the mutual fund business is.

A GAO report released in July cites data from Strategic Insight, a New York-based fund research firm, showing that profit margins for 18 publicly held asset management firms grew from 33 percent in 1995 to 36 percent in 1998.

The GAO also says return on equity for nine of the firms ranged from 23 percent to 26 percent over the period, versus an average of 22 percent for companies in the S&P 500 index.

Still, some experts aren't satisfied with these numbers. Harvard Business School professor Michael Porter says he's frustrated by the lack of information.

"I don't know what the average profitability in the industry is, because you all [in the fund industry], cleverly don't disclose it," Porter said in May during a presentation at the annual meeting of the Investment Company Institute (ICI), a Washington, D.C.-based trade group for fund companies.

Why is fund sponsorship profitability data so hard to find?

ICI spokesperson John Collins says it's difficult to separate financial data on fund sponsorship activities from information on other investment management services provided by ICI member firms.

Jeff Keil, vice president of portfolio evaluation, performance and board reporting at Lipper Inc., agrees. Keil says the elusiveness of these figures has more to do with the nature of the industry than any attempt to keep profitability statistics quiet.

"It's not the desire of anyone in the business to blend those numbers so they get lost in the shuffle," Keil claims.

Lipper Inc. analyzed profit margins for 10 investment management firms as a whole (not just the firm's fund operations). The researcher estimates that the average profit margin for fund companies in 1999 was 30.3 percent, which includes marketing revenues and expenses.