Demand for farm products rises and falls as national income rises and falls. But the demand for some farm products has been rising with the income. Meanwhile the demand for other farm products has been falling.
Shepherd, Geoffrey S.
"Why Did the Demand for Meat Go Up and Butter Down?,"
Iowa Farm Science: Vol. 4
, Article 7.
Available at: https://lib.dr.iastate.edu/farmscience/vol4/iss2/7