大不況が起きた原因は何
The prices of agricultural products began to decline after WW I and eventually many farmers were forced out of business, causing the failure of hundreds of small rural banks. Agricultural productivity resulting from tractors, fertilizers and hybrid corn was only part of the problem; the other problem was the change over from horses and mules to internal combustion transportation. The horse and mule population began declining after WW 1, freeing up enormous quantities of land previously used for animal feed.
The prices of agricultural products began to decline