The Bill Gross stamp index

The Newport Beach-based guru of bond trading made news a couple of weeks back with word that he was auctioning off his collection of classic British stamps, and then donate the proceeds, roughly $4 million to $5 million, to Doctors Without Borders. Now for some details: Gross says he paid about $2 million for the stamps, mainly between 1998 and 2000. That's a pretty fair return, and Gross says it's not just based on the escalating value of collectibles. It's based on a system. Here's how it's explained in the Wealth Report:

Studying patterns in the stamp market over the past 75 years, Mr. Gross found that certain sales tracked closely the growth in U.S. nominal gross domestic product. By projecting future GDP growth, he could also plot the future prices for certain stamps. "I looked at the history of the stamps and correlated the prices to the growth rate of the U.S. economy to make sure I wasn't getting my hat handed to me," he says. "I don't think most of the people in the stamp-collecting world understood what I was doing." He's also a clever trader, having swapped some 1918 "Inverted Jenny" stamps for an 1868 Benjamin Franklin "Z-grill" to give him every stamp the U.S. has ever produced. Yet Mr. Gross says that rich collectors like him have pushed up prices in the stamp market so fast that he's worried it could be near a peak. That was one reason he decided to sell part of his collection and take some profits off the table to benefit Doctors Without Borders.