Keynesian economics ( KAYN-zee-ən; sometimes Keynesianism, named after British economist John Maynard Keynes) are the various macroeconomic theories and models of how aggregate demand (total spending in the economy) strongly influences economic output and inflation. In the Keynesian view, aggregate demand does not necessarily equal the productive capacity of the economy. It is influenced by a host of factors that sometimes behave erratically and impact production, employment, and inflation. Keynesian economists generally argue that aggregate demand is volatile and unstable and that, consequently, a market economy often experiences inefficient macroeconomic outcomes, including recessions when demand is too low and inflation when demand is too high. Further, they argue that these economic fluctuations can be mitigated by economic policy responses coordinated between a government and their central bank. In particular, fiscal policy actions taken by the government and monetary policy actions taken by the central bank, can help stabilize economic output, inflation, and unemployment over the business cycle. Keynesian economists generally advocate a regulated market economy – predominantly private sector, but with an active role for government intervention during recessions and depressions. Keynesian economics developed during and after the Great Depression from the ideas presented by Keynes in his 1936 book, The General Theory of Employment, Interest and Money. Keynes' approach was a stark contrast to the aggregate supply-focused classical economics that preceded his book. Interpreting Keynes's work is a contentious topic, and several schools of economic thought claim his legacy. Keynesian economics has developed new directions to study wider social and institutional patterns during the past several decades. Post-Keynesian and New Keynesian economists have developed Keynesian thought by adding concepts about income distribution and labour market frictions and institutional reform. Keynesian economics, as part of the neoclassical synthesis, served as the standard macroeconomic model in the developed nations during the later part of the Great Depression, World War II, and the post-war economic expansion (1945–1973). It was developed in part to attempt to explain the Great Depression and to help economists understand future crises. It lost substantial influence following the oil shock and resulting stagflation of the 1970s, with neoliberalism largely replacing Keynesianism as the dominant economic paradigm starting in the late 1970s. Keynesian economics was later redeveloped as New Keynesian economics, becoming part of the contemporary new neoclassical synthesis, that forms current-day mainstream macroeconomics. Today, governments still tend to use Keynesian or otherwise interventionist tools during major crises; the 2008 financial crisis sparked the 2008–2009 Keynesian resurgence by governments around the world. Critics from the Austrian school (such as Friedrich Hayek and Ludwig von Mises) and monetarists (such as Milton Friedman) have argued that Keynesian policies distort market price signals through artificial credit expansion and deficit spending, leading to malinvestment, inflation, unsustainable public debt, and prolonged business cycles rather than genuine stabilization.
Historical context
Pre-Keynesian macroeconomics Macroeconomics is the study of the factors applying to an economy as a whole. Important macroeconomic variables include the overall price level, the interest rate, the level of employment, and income (or equivalently output) measured in real terms. The classical tradition of partial equilibrium theory had been to split the economy into separate markets, each of whose equilibrium conditions could be stated as a single equation determining a single variable. The theoretical apparatus of supply and demand curves developed by Fleeming Jenkin and Alfred Marshall provided a unified mathematical basis for this approach, which the Lausanne School generalized to general equilibrium theory. For macroeconomics, relevant partial theories included the Quantity theory of money determining the price level and the classical theory of the interest rate. In regards to employment, the condition referred to by Keynes as the "first postulate of classical economics" stated that the wage is equal to the marginal product, which is a direct application of the marginalist principles developed during the nineteenth century (see The General Theory). Keynes sought to supplant all three aspects of the classical theory.
Precursors of Keynesianism
Although Keynes's work was crystallized and given impetus by the advent of the Great Depression, it was part of a long-running debate within economics over the existence and nature of general gluts. A number of the policies Keynes advocated to address the Great Depression (notably government deficit spending at times of low private investment or consumption), and many of the theoretical ideas he proposed (effective demand, the multiplier, the paradox of thrift), had been advanced by authors in the 19th and early 20th centuries. (E.g. J. M. Robertson raised the paradox of thrift in 1892.) Keynes's unique contribution was to provide a general theory of these, which proved acceptable to the economic establishment. An intellectual precursor of Keynesian economics was underconsumption theories associated with John Law, Thomas Malthus, the Birmingham School of Thomas Attwood, and the American economists William Trufant Foster and Waddill Catchings, who were influential in the 1920s and 1930s. Underconsumptionists were, like Keynes after them, concerned with failure of aggregate demand to attain potential output, calling this "underconsumption" (focusing on the demand side), rather than "overproduction" (which would focus on the supply side), and advocating economic interventionism. Keynes specifically discussed underconsumption (which he wrote "under-consumption") in the General Theory, in Chapter 22, Section IV and Chapter 23, Section VII. Numerous concepts were developed earlier and independently of Keynes by the Stockholm school during the 1930s; these accomplishments were described in a 1937 article, published in response to the 1936 General Theory, sharing the Swedish discoveries.
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