The long-run trend of the ratio between beef cattle prices and hog prices at Chicago has been rising since 1910 at the rate of about 1.2 percent per year.

The principal cause of this change has been an increase in the demand for beef and a decrease in the demand for pork, relative to total disposable consumer income. An additional reason has been a decline in the relative value of lard.

The reasons why these' changes took place are several: (1) The percentage of urban consumers (who eat more than twice as much beef per capita as farm consumers) in the population of the United States rose. (2) Rural and urban occupations both became less muscular, decreasing our consumption of carbohydrate foods and leaving room for an increase in our demand for meat. Incomes rose, and most of the increase in the demand for meat was focused on beef. for the income-elasticity of the demand for beef is 2.5 times as high as the elasticity for pork. (3) Income in the United States became more evenly distributed. (4) Vegetable oils offered increased competition with lard.