Farmers who plant based on last year's price can keep prices swinging forever

If hog farmers breed more pigs after a year of high prices, the resulting glut crashes the price — so next year they breed fewer, creating a shortage that sends prices back up. The Cobweb Theorem formalizes why livestock and crop prices can cycle for years without ever settling, tracing a zigzag on a supply-and-demand graph.

— Mordecai Ezekiel, The Cobweb Theorem — Quarterly Journal of Economics, vol. 52, 1938