Greenspan reasons that because hardly anyone actually sees a guy's undies, they're the first thing men stop buying when the economy tightens. (He told this to National Public Radio's Robert Krulwich years ago.)
By extension, pent-up demand means underwear sales should be among the early risers when growth returns and consumers feel confident enough to shrug off "frugal fatigue," says Marshal Cohen, the chief industry analyst with NPD Group, which tracks consumer behavior.
So now we know:
1. Collect underpants
2. Examine their condition, and use the degree of wear as a leading indicator of the price of risky assets, guiding your investment decisions.