Which economist developed an economic theory that became influential during the global depression as well as the rest of the twentieth century

John Maynard Keynes was a major historical economist who was made famous in the early part of the 20th century. He is considered the father of modern macroeconomics and his work has informed governments and thinkers for decades since this time. He challenged neoclassical economic theory which asserted that the market would correct itself to achieve full employment if workers would adjust to changes in wages. Instead Keynes asserted that this would not occur and that instead government intervention into the economy was necessary to deal with the booms and busts of the economic cycle.