Keynesian economics (pronounced /ˈkeɪnzjən/), also called Keynesianism, or Keynesian Theory, is an economic theory based on the ideas of 20th century British economist John Maynard Keynes (pictured). Keynesian economics promotes a mixed economy, where both the state and the private sector play an important role. Keynesian economics differs markedly from laissez-faire economics (economic theory based on the belief that markets and the private sector operate well on their own, without state intervention).
In Keynes's theory, general (macro-level) trends can overwhelm the micro-level behavior of individuals. Instead of the economic process being based on continuous improvement in potential output, as most classical economists had believed from the late 18th century on, Keynes asserted the importance of aggregate demand for goods as the driving factor of the economy, especially in periods of downturn. From this he argued that government policies could be used to promote demand at a macro level, to fight high unemployment and deflation of the sort seen during the 1930s. A central conclusion of Keynesian economics is that there is no strong automatic tendency for output and employment to move toward full employment levels. This conclusion conflicts with the tenets of classical economics, and those schools, such as supply-side economics or the Austrian School, which assume a general tendency towards a welcome equilibrium in a restrained money-creating economy. In neoclassical economics, which combines Keynesian macro concepts with a micro foundation, the conditions of General equilibrium allow for price adjustment to achieve this goal.