The cooperative marketing of livestock has had a greater growth than perhaps any other form of cooperative endeavor. Using Iowa as an illustration, the oldest association in the state in 1920 was organized in 1904. Of all the associations in existence in the state in 1920, about 3 percent were organized before 1910, only 8 percent before 1915, and less than 25 percent before 1918. About 75 percent of the associations in existence in December, 1920, were organized during the years 1919 and 1920.*