Some curious everyday products can be strong signs of economic conditions. For example, Alan Greenspan once told NPR's Robert Krulwich that men's underwear sales are a strong indicator --sales are usually flat, so if they go down, the economy is in trouble. So what's the flip side? Donuts, of course . Or at least that's what retailers Krispy Kreme and Dunkin Donuts have found. Dunkin Donuts has shifted its marketing strategy to put the focus back on the donut: