The fact that is the BEST piece of supporting evidence that overproduction and falling prices was a cause of the Great Depression is that in 1920 a bushel of wheat sold for $2.94, in 1929 it sold for $1.00 and by 1932 a bushel sold for .30 cents. Farmers produced more as a result of WWI but as demand went down, they continued to overproduce which led to falling prices.