hemline theory

hemline theory (uncountable)

1. The informal theory that stock market prices move in the same direction as the hemline of women's skirts, short skirts being considered bullish and long skirts bearish.
   • 1986 February 3, John Gantz, “Stock Market Is Easy if You Choose the Right Omen”, in InfoWorld, InfoWorld Media Group, Inc., page 19:

     I also like the hemline theory better than the freight-car-loading theory, on the grounds of aesthetics. The former theory, you will recall, relates stock booms to periods in which hemlines are higher.