An agrarian society is a society that depends on agriculture as its primary means for support and sustenance. The society acknowledges other means of livelihood and work habits but stresses the importance of agriculture and farming, and was the most common form of socio-economic oganization for most of recorded human history. This was the common way for Medieval European countries to gain wealth. Change in agrarian practices occurred first in England in the 18th century, with the British Agricultural Revolution, and then subsequently later spread to the rest of Europe and the United States. Thomas Jefferson promoted an agrarian society for the United States during the nation's early formation. One modern example of a national agrarian experiment exists: the tyrannical efforts of the Khmer Rouge in Cambodia from 1975 to their deposition by nam in 1979. Sub-national agrarian movements include the Amish and Mennonites.