Likewise, the farmer populations worked the system of collective farms to grow food to feed the industrial workers in the industrialised cities. Since the mid-1930s, Marxism–Leninism has advocated an austere social-equality based upon asceticism, egalitarianism and self-sacrifice. In the 1920s, the Bolshevik party semi-officially allowed some limited, small-scale wage inequality to boost labour productivity in the economy of the Soviet Union. These reforms were promoted to encourage materialism and acquisitiveness in order to stimulate economic growth. This pro-consumerist policy has been advanced on the lines of industrial pragmatism as it advances economic progress through bolstering industrialisation. In the economic praxis of Bolshevik Russia, there was a defining difference of political economy between socialism and communism. Lenin explained their conceptual similarity to Marx's descriptions of the lower-stage and the upper-stage of economic development, namely that immediately after a proletarian revolution in the socialist lower-stage society the practical economy must be based upon the individual labour contributed by men and women and that paid labour would be the basis of the communist upper-stage society that has realised the social precept of the slogan: "From each according to his ability, to each according to his needs". Marxism–Leninism aims to create an international communist society. It opposes colonialism and imperialism and advocates decolonisation and anti-colonial forces. It supports anti-fascist international alliances and has advocated the creation of popular fronts between communist and non-communist anti-fascists against strong fascist movements. This Marxist–Leninist approach to international relations derives from the analyses (political, economic, sociological and geopolitical) that Lenin presented in the essay "Imperialism, the Highest Stage of Capitalism" (1917). Extrapolating from five philosophical bases of Marxism, namely that human history is the history of class struggle between a ruling class and an exploited class; that capitalism creates antagonistic social classes, i.e. the bourgeois exploiters and the exploited proletariat; that capitalism employs nationalist war to further private economic expansion; that socialism is an economic system that voids social classes through public ownership of the means of production and so will eliminate the economic causes of war; and that once the state (socialist or communist) withers away, so shall international relations wither away because they are projections of national economic forces, Lenin said that the capitalists' exhaustion of domestic sources of investment profit by way of price-fixing trusts and cartels, then prompts the same capitalists to export investment capital to undeveloped countries to finance the exploitation of natural resources and the native populations and to create new markets.