As chairman of the Federal Reserve, Alan Greenspan was known for using quirky, proletariat metrics to judge the temperature of the economy. The most famous of these, as recounted by NPR's Robert Krulwich in January 2008, were the sales of men's underwear. If the economic scales dipped even the slightest, Greenspan reasoned, it was as sure a sign as any that people were truly feeling the pinch.

"If you look at sales of male underpants it's...