The chief occupation of the people is agriculture, with the vast majority engaged in rice farming. In years with normal harvests, Laos is self-sufficient in rice production, a reflection of the success of private land ownership and market incentives. In addition to a variety of food crops, modest amounts of such cash crops as sugarcane, tobacco, and coffee are produced. Agricultural production, however, is vulnerable to natural calamities, and Laos is subject to periodic droughts and floods, with both sometimes occurring in the same year. A significant proportion of rice production comes from upland dry rice raised by hill people using shifting-cultivation methods (i.e., fields are cleared and cultivated for a few years before being abandoned and allowed to revert to forest). The government has considered this practice to be a major cause of deforestation and has attempted to resettle hill peoples on plains where they can adopt sedentary agricultural practices.