Bangladesh became independent in 1971 following a nine-month-long War of Liberation which devastated the material economic base of the country. Reconstruction efforts began immediately following the war and were consolidated within the framework of the First Five-Year Plan launched in 1973. The country consists of 144,000 square kilometres of low deltaic land in the confluence of two major rivers of the world, the Ganges and Brahmaputra. The area is highly disaster-prone, being subject to recurrent floods and cyclones. It is the most densely populated country in the world with a population of 70 million in 1971 and 108 million in 1991. The population density at present is 750 persons per square kilometre. The country has a poor natural resource base: except for limited gas and coal reserves, it has no other known natural resource. With a per capita income of US$180, a very low domestic saving rate and a large external debt, Bangladesh faces an extremely difficult development challenge.