The agricultural sector employs 83% of the labor force and contributes 56% of the GDP. Only 12% of the total land area is under permanent or seasonal cultivation. The country is divided into three major regions according to the water requirements of the major crops. On the coast and in river estuaries is the palm-tree (coconut) zone; rice is the predominant crop of the intermediary marshy areas; and peanuts are grown in the sandy areas of the interior. Rice is the major staple crop; corn, millet, and sorghum are also produced and consumed very widely. In the 1950s, Guinea-Bissau exported about 40,000 tons of rice per year; since 1962, rice has been imported, as frequent droughts often cause crop failure. In 1999, Guinea-Bissau produced 130,000 tons of rice, 30,000 tons of millet, 18,000 tons of peanuts, 44,000 tons of coconuts, 38,000 tons of cashew nuts, and 8,000 tons of palm kernels. Palm kernels, cashew nuts, and peanuts are the most important export crops. The war which culminated with independence in 1974 left the economy in shambles, reducing crop output by over one-third. Public investment, financed heavily by external borrowing, neglected agriculture to focus on the manufacturing sector. Agricultural recovery was hampered by inappropriate pricing policies, an overvalued exchange rate, and an inefficient marketing system. This policy has now been changed through price liberalization, so that some important goods like rice are now traded informally with neighboring countries. In 2001, trade in agricultural products consisted of $37.8 in imports and $71.5 million in exports.