(MONEY Magazine) – Why does the world know that Bill Gross has been selling some of his personal stake in Pimco Total Return? Only because he decided to say something in public. (And thanks for the heads-up, Bill.) There's no law that says fund managers have to disclose their holdings or their trades. "Mutual fund investors don't have equivalent disclosure to what stock investors have been getting for years," says Russel Kinnel, director of fund research for Morningstar.

Currently, only mutual fund directors--who sometimes double as managers--are required to fess up to their personal holdings in the funds they oversee. You can find that info in a document called the "statement of additional information," but most fund companies do not routinely send SAIs to their shareholders. (Enterprising investors can find them on the EDGAR database at www.sec.gov or call the fund company.)

A bill passed in November by the House of Representatives would require managers to disclose their "ownership interest" in their fund. But the legislation, now before the Senate, doesn't specify how this would be disclosed, or how often. The SEC is also signaling that it will require more disclosure.

Better disclosure would not only give investors a hint at their managers' thinking--it could be a red flag for the kind of trading violations that have roiled the industry. "The Putnam case shows that the ideal disclosure would be a record of all their transactions over the year in the fund," Kinnel says. Mercer Bullard, of advocacy group Fund Democracy, would like to see how much the manager holds in the fund as a dollar figure and as a percentage of net worth. --MEGAN JOHNSTON