The Men’s Underwear Index:

It’s a quirky economic indicator that implies that sales of men’s underwear correlate with the health of the economy. In times of economic recession, men’s underwear sales are believed to slow as people delay buying non-necessities, whereas an upswing in the economy should come with higher sales. This is predicated on the belief that underwear is something one needs, and during economic downturns, buying is postponed, but as the economy picks up, discretionary spending also picks up, and this includes for products like underwear. Explanation:
The Indicator:
Men’s Underwear Index implies that men’s underwear sales are a stand-in for consumer optimism and discretionary expenditure.
Economic Slump:
In recession or economic depression, consumers reduce discretionary spending, including men’s undergarments.
Economic Recovery:
As the economy picks up, customers get back confidence and begin to spend more, resulting in higher underwear sales.