Based on a system of plantation slavery, the social structure of the South was far more stratified and patriarchal than that of the North. In 1850 there were around 350,000 slaveholders in a total free Southern population of about six million. Among slaveholders, the concentration of slave ownership was unevenly distributed. Perhaps around 7 percent of slaveholders owned roughly three-quarters of the slave population. The largest slaveholders, generally owners of large plantations, represented the top stratum of Southern society. They benefited from economies of scale and needed large numbers of slaves on big plantations to produce cotton, a highly profitable labor-intensive crop.