The primary constraint on export agriculture had always been external, especially as structures for controlling the internal problems of land and labor were developed during the colonial and coffee transformations. The postwar expansion of Central American export agriculture is the latest in a sequence of stages that have reinforced the region's linkage to the international economic system. Trade in agricultural commodities was part of pre-Conquest economic life. The postwar expansion of agricultural exports furthered the region's integration into the international system as a larger share of the population became more dependent on the success of agricultural exports and/or the availability of agricultural imports, from wheat to fertilizer. The desire of public and private elites in Central America to find new agricultural exports intensified after World War II. In 1972 the cattle sector in Costa Rica received more credits than the rest of agriculture combined.