The development over the last half-century of the present Cameroon economy has hinged on expansion of primary exports. These export crops were initially produced mainly on plantations but increasingly they are produced by African commercial farmers. The expansion of output was based on the utilization of previously unused land and labour and on the introduction of new products (largely tree crops) employing labour intensive techniques. A limited volume of transport, commercial, and administrative infrastructure was built up mainly in the southwestern sixth of the territory. A typical 'opening up' export boom was interrupted by World War I but started again afterwards in the East under French colonial development policy. In the West, plantations (largely privately owned German ones in the interwar period and state owned ones later under the Cameroon Development Corporation) remained dominant and the sketchy British mandatory administration and the Lagos-Accra centred commercial interests failed to stimulate any very substantial growth in African production or in public revenue.