Sonin, a Soviet author, in 1959, demonstrate the rapid urbanization of the USSR. Between 1939 and 1959, the rural population declined by 21.3 million, while that of urban centers increased by 39.4 million. Of this dramatic shift in population, rural flight accounts for more than 60% of the change. Generally, most rural migrants tended to settle in cities and towns within their district. Rural flight persisted through the majority of the 20th century. However, with the end of the Soviet Union, rural flight reversed as political and economic instability in the cities prompted many urban dwellers to return to rural villages. Rural flight did not occur uniformly throughout the USSR. Western Russia and the Ukraine experienced the greatest declines in rural population, 30% and 17% respectively. Conversely, peripheral regions of the USSR, like Central Asia, experienced gains, contradicting the general pattern of rural-urban migration of this period. Increased diversification of crops and labor shortages were primary contributors to the gains in rural population in the periphery. Rural flight in Russia and the former USSR had several major determinants. The industrialization of agriculture, which came later in Russia and the former USSR, led to declines in available rural jobs. Lower living standards and tough work also motivated some peasants to migrate to urban areas. In particular, the Soviet kolkhoz system (the collective farms in the Soviet Union) aided in maintaining low living standards for Soviet peasants. Beginning around 1928, the kolkhoz system replaced family farms throughout the Soviet Union. Forced to work long hours for low pay at rates fixed by the government and often unadjusted to inflation, Russian peasants experienced quite low living-conditions - especially compared to urban life. While Brezhnev's wage reforms in 1965 ameliorated the low wages received by peasants, rural life remained suffocating, especially for the skilled and the educated. Although migrants came from all segments of society, several groups were more likely to migrate than others. Like other examples of rural flight, the young were more likely than the old to migrate to the cities. Young women under 20 were the most likely segment of the population to leave rural life. This exodus of young women further exacerbated the demographic transitions occurring in rural communities as the rate of natural increase dropped precipitously over the course of the 20th century. Lastly, the skilled and educated were also likely to migrate to urban areas. Mexico Rural flight