The early 1960s witnessed significant changes in the commodity structure of Mainland China's international trade. One of the most striking developments during these years was that China became a net food importer, whereas in the 1950s, when Russia was her most important trading partner, China had been a net exporter of foodstuffs, and roughly one third to one half of China's exports to the Soviet Union had consisted of processed and unprocessed food. These exports were reduced to a mere 3 to 5 per cent, of China's total exports to Russia during 1961–63. Accompanying this change was a pronounced increase of China's imports of food from western countries. During 1952–60, China's purchase of “cereals and cereal preparations” had accounted for but 1 per cent, or less of her total imports from the West. This was augmented to approximately one-half of total imports in 1961–63, about one-third in 1964–66 and roughly one-fifth in 1967. The single most important item of the imported food has been wheat, amounting to four to five million metric tons a year since 1961, and coming mostly from Canada, Australia, Argentina and France.