In 1948 some farmers experienced the sharpest drop in farm income in 15 years. But the level is still a lot higher than in 1940.
Howell, H. B.
"Lets Look At the Records- What About Farm Income?,"
Iowa Farm Science: Vol. 4
, Article 4.
Available at: https://lib.dr.iastate.edu/farmscience/vol4/iss5/4