a sugar refinery. Other aid donors were the Soviet Union, Yugoslavia, France, the Federal Republic of Germany (West Germany), Japan, and Australia. United States economic assistance to Cambodia amounted to more than US$350 million for the 1955 to 1962 period, and it was invested mostly in the areas of public health, education, and agricultural development. To avoid the appearance of undue dependence upon foreign aid, Cambodia insisted upon "project sharing," that is, participation of its own in specific enterprises, such as the French-sponsored oil refinery and truck assembly plant at Sihanoukville. This stipulation imposed by Phnom Penh also had the effect of holding down the scale of many aid projects and the amounts of loans extended to the Cambodian government. The government also used foreign assistance to expand the country's transportation and communication networks. France helped to develop Sihanoukville, Cambodia's second largest port, which opened in 1960, and the United States constructed a highway linking the port to Phnom Penh. In addition, the Cambodians, with French and West German assistance, built a railway from Sihanoukville to the capital. Despite Sihanouk's claims of economic progress, Cambodia's industrial output in 1968 amounted to only 12 percent of GNP, or only one-third of agricultural production. Rice and rubber were the country's two principal commodity exports and foreign-exchange earners during the Sihanouk era. Wartime economy (1970–1975) The war that engulfed the rest of Indochina spread to Cambodia in April 1970, shortly after the coup that deposed Prince Sihanouk. Wartime conditions had a major impact on the country's economy, especially on the export sector. Production and export of virtually all commodities dropped sharply, as insecurity spread throughout the countryside. Intense combat in the nation's most densely populated farming areas caused a large segment of the peasant population to flee to cities and to towns. By 1975 the population of Phnom Penh had swollen to 2 million, from just 50,000 in 1955. Moreover, the war seriously dislocated the economic system. Food shortages arose as insurgents interrupted the transportation of crops from the countryside to the main marketing centers. Increasing budgetary expenditures, skyrocketing inflation, shrinking export earnings, and a rising balance-of-payments deficit plagued the war-torn economy. The war's most damaging effect was on rice production. In 1972 Cambodia needed to import rice (from Japan and from Thailand) for the first time since independence. Fighting reduced the amount of land under rice cultivation to fewer than 800,000 hectares