Most mornings I am confronted with a choice of what to eat for breakfast. As a semi-rational individual, one would assume I would seek to maximise my benefits while minimising opportunity costs when making this choice.
Prior to 1978 in China, communal farmland was assigned to individuals to work for the government. Farmers gave anything that they produced from their land to the government, which then distributed the crops out to the people. Agricultural land was less productive in 1978 than it had been in 1949, when the communists took over. This was because the farmers did not have any incentive to produce more than the minimum; any extra work would result in the same food rations from the government.