Colonies such as Nigeria became part of British imperial expansion that focused on exploiting raw materials, minerals, and foodstuffs important to Western industrial development. Britain tried to encourage tropical export crops in Nigeria and to stimulate demand there for British manufactured goods. The colonies built a railroad network between the 1890s and World War II, and constructed roads at an accelerating rate after the 1930s. These developments, along with the introduction of the pound sterling as the universal medium of exchange, encouraged export trade in tin, cotton, cocoa, groundnuts, and palm oil. Britain maintained its economic hegemony over the colonies through military power, strategic alliances, and the collaboration of indigenous rulers.
Data as of June 1991