The “Great Leap Forward” began after the end of the “Anti-Rightist Movement” and coincided with a period of increasing political tension between China and the Soviet Union. It was the main cause of the severe Great Chinese Famine, which lasted from 1959 to 1961. Due to the forced collectivisation of agriculture, the additional burden placed on farmers by work on infrastructure and industrialisation projects and an internal migration of the rural population to the cities, agricultural yields fell from 1959 to 1961. At the same time, the grain levies expected by the state as a tax and for export were greatly increased and enforced with coercive measures. The number of victims of this famine is estimated at between 14 and 55 million people, making it the deadliest famine in history. In addition to famine-related deaths, millions also died from beatings, torture and executions. More than thirty per cent of all homes were destroyed during the campaign for various reasons.

Wikipedia - Großer Sprung nach vorn (in German, translated)

The Great Leap was one of two periods between 1953 and 1976 in which China’s economy shrank (the other being the Cultural Revolution). Economist Dwight Perkins argues that “enormous amounts of investment only produced modest increases in production or none at all. … In short, the Great Leap [Forward] was a very expensive disaster”.

Wikipedia - Great Leap Forward