It's called the Men's Underwear Index, and it may be the simplest and yet most ingenious gauge of consumer confidence that I've ever heard. Simply put:

Sales of men's underwear typically are stable because they rank as a necessity. But during times of severe financial strain, men will try to stretch the time between buying new pairs, causing underwear sales to dip. "It's a prolonged purchase," said Marshal Cohen, senior analyst with the consumer research firm NPD Group. "It's like trying to drive your car an extra 10,000 miles."

So, according to the theory, when men start buying underwear again, it's a sign that they believe better times may be coming. And that's exactly what's happening.

Retailers are reporting encouraging signs in the men's underwear department. Sears spokeswoman Amy Dimond said stores are beginning to see more sales. At Target, spokeswoman Jana O'Leary said sales of men's underwear have been stronger over the past two months and multi-pair packs are moving. No less an oracle than former Federal Reserve chairman Alan Greenspan has given this theory credence, as described in a report on NPR two years ago.

For the record, I stocked up in July, which, come to think of it, was right around the time we were closing our very healthy September issue.