John Maynard Keynes, 1st Baron Keynes, CB, FBA was a British economist whose ideas have profoundly affected the theory and practice of modern macroeconomics, and informed the economic policies of governments. He built on and greatly refined earlier work on the causes of business cycles, and is widely considered to be one of the founders of modern macroeconomics and the most influential economist of the 20th century. His ideas are the basis for the school of thought known as Keynesian economics, as well as its various offshoots.
In the 1930s, Keynes spearheaded a revolution in economic thinking, overturning the older ideas of neoclassical economics that held that free markets would, in the short to medium term, automatically provide full employment, as long as workers were flexible in their wage demands. Keynes instead argued that aggregate demand determined the overall level of economic activity, and that inadequate aggregate demand could lead to prolonged periods of high unemployment. He advocated the use of fiscal and monetary measures to mitigate the adverse effects of economic recessions and depressions. Following the outbreak of the Second World War, Keynes's ideas concerning economic policy were adopted by leading Western economies. In 1942, Keynes was awarded a hereditary peerage as Baron Keynes of Tilton in the County of Sussex. During the 1950s and 1960s, the success of Keynesian economics resulted in almost all capitalist governments adopting its policy recommendations.