Gates' investment diversification has made his net worth difficult to verify.

"Also, since real estate prices do not move in tandem with stock and bond values, real estate provides an effective means of investment diversification."

Internet domains are perceived as an alternate asset class for investment diversification.

The reason, according to the study, is investment diversification: large investors can offset losses on stocks that fell as a result of fraud with gains on shares of other companies that might have inflated prices as a result of a fraud that has not yet been disclosed.

And such concentration flies in the face of commonly held wisdom about the importance of investment diversification.

Is investment diversification important?

With investment diversification, it's OK if some of your assets do poorly each year.

The purpose of investment diversification is to spread out your investment risk and balance it among (and within) the different asset classes: stocks, bonds and cash.

Her father is a vice president of the Intersec Research Corporation, a consulting company in international investment diversification in Stamford, Conn.