border. The cultivation of rubber and of corn were economically important, and the former was a response to the high market demand. This shift to producing commodities transformed the economy. Production techniques changed as a response to the need of more intensive factor inputs. The prosperous 1920s, when rubber, rice, and corn were in demand overseas, were years of considerable economic growth, but the world depression after 1929 caused great suffering, especially among rice cultivators whose falling incomes made them more than ever the victims of moneylenders. Industry was rudimentary and was designed primarily to process raw materials such as rubber for local use or export. There was considerable immigration, which created a plural society similar to those of other Southeast Asian countries. As in British Burma and British Malaya, foreigners dominated the developed sectors of the economy. Vietnamese people came to serve as laborers on rubber plantations and as clerical workers in the government. As their numbers increased, Vietnamese immigrants also began to play important roles in the economy as fishermen and as operators of small businesses. Chinese people had been in Cambodia for several centuries before the imposition of French rule, and they had dominated precolonial commerce. This arrangement continued under the French, because the colonial government placed no restrictions on the occupations in which they could engage. Chinese merchants and bankers in Cambodia developed commercial networks that extended throughout Indochina as well as overseas to other parts of Southeast Asia and to mainland China. Economic developments after independence The predominance of agriculture and the lack—or neglect—of real industrial development have characterized Cambodia's modern economy since independence in 1953. Wet rice cultivation traditionally has played a key role in peasant subsistence, in national self-sufficiency in food production, in trade relations with other states, and in governmental revenues for national development. Conversely, the government has made few attempts to industrialize the nation, acquiesced to a pragmatic combination of socialism and small-scale capitalism, and the country achieved some limited rehabilitative goals. Cambodia's economy struggled to keep up with other countries in Southeast Asia due to the problems in developing its human and physical infrastructure. This is indicated by a relatively low exports per capita level. In the late 1980s, government policies fundamentally relied upon the nation's own sparse resources—chiefly agriculture, a nascent industrial base, and modest foreign aid from Comecon countries and nongovernmental international organizations. The level of exports per