“On average, a U.S. dairy cow produced 9,193 kg (20,267 lb) of milk in 2007, more than double the per-cow milk yield in 1967 and 47% more than the per-cow milk yield in 1987. . . . Even though the number of cows in the dairy industry declined from 1987 to 2007, the total production of milk increased by 30%.”20
