John Maynard Keynes was a British economist whose ideas have profoundly affected the theory and practice of modern macroeconomics, as well as the economic policies of governments. He identified the causes of business cycles, and advocated the use of fiscal and monetary measures to mitigate the adverse effects of economic recessions and depressions. His ideas are the basis for the school of thought known as Keynesian economics, and 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 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. Following the outbreak of World War II, Keynes's ideas concerning economic policy were adopted by leading Western economies. During the 1950s and 1960s, the success of Keynesian economics resulted in almost all capitalist governments adopting its policy recommendations, promoting the cause of social liberalism.
Keynes's influence waned in the 1970s, partly as a result of problems that began to afflict the Anglo-American economies from the start of the decade, and partly because of critiques from Milton Friedman and other economists who were pessimistic about the ability of governments to regulate the business cycle with fiscal policy.
However, the advent of the global financial crisis in 2007 has caused a resurgence in Keynesian thought. Keynesian economics has provided the theoretical underpinning for the economic policies of President Barack Obama of the United States, former Prime Minister Gordon Brown of the United Kingdom, and other global leaders to ease the late 2000s economic recession.
Keynes is widely considered to be the father of modern macroeconomics, and by various commentators such as economist John Sloman, the most influential economist of the 20th century. In 1999, Time magazine included Keynes in their list of the 100 most important and influential people of the 20th century, commenting that; "His radical idea that governments should spend money they don't have may have saved capitalism". In addition to being an economist, Keynes was also a civil servant, a director of the Bank of England, a patron of the arts and an art collector, a part of the Bloomsbury Group of intellectuals, an advisor to several charitable trusts, a writer, a private investor, and a farmer. In 1925, he married the Russian ballerina Lydia Lopokova, but remained childless.