Agriculture is the mainstay of the Cambodian economy. Agriculture accounted for 90 percent of GDP in 1985 and employed approximately 80 percent of the workforce. Rice is the principal commodity. Major secondary crops include maize, cassava, sweet potatoes, groundnuts, soybeans, sesame seeds, dry beans, and rubber. The principal commercial crop is rubber. In the 1980s it was an important primary commodity, second only to rice, and one of the country's few sources of foreign exchange.