also called Keynesianism, or Keynesian Theory, is an economic theory based on the ideas of the 20th-century British economist John Maynard Keynes. Keynesian economics promotes a mixed economy, in which both the stateand the private sector are considered to play an important role. Keynesian economics markedly differs from, and sought to provide solutions to what some economists believed to be the failure oflaissez-faire economic liberalism (which advocates that markets and the private sector operate best without state intervention).
In Keynes's theory, macroeconomic 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 1700s 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 amacro level, to fight high unemployment and deflation of the sort seen during the 1930s. This is in contrast to supply-side economics. Keynes believed that the government was responsible for helping to pull a country out of a depression. If the government increases its spending, then the citizens are encouraged to spend more because more money is in circulation. People will start to invest more, and the economy will climb back up to normal.
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 the 'neoclassical synthesis', which combines Keynesian macro concepts with a micro foundation, the conditions of General equilibrium allow for price adjustment to achieve this goal.
More broadly, Keynes saw his as a general theory, in which utilization of resources could be high or low, whereas previous economics focused on the particular case of full utilization.
Keynes was very critical of rentiers and speculators, from a somewhat Fabianperspective.
His experience with the Treaty of Versailles pushed him to break with previous theories. His The Economic Consequences of the Peace (1920) not only recounted the general economics, as he saw them, of the Treaty, but the individuals involved in making it. The book established him as an economist who had the practical political skills to influence policy. In the 1920s, Keynes published a series of books and articles which focused on the effects of state power and large economic trends, developing the idea of monetary policy as something separate from merely maintaining currency against a fixed peg. He increasingly believed that economic systems would not automatically right themselves to attain "the optimal level of production." This is expressed in his famous quote, "In the long run, we are all dead," implying that it does not matter that optimal production levels are attained in the long run, because it would be a very long run indeed.
In the late 1920s, the world economic system began to break down, after the shaky recovery that followed World War I. With the global drop in production, critics of the gold standard, market self-correction, and production-driven paradigms of economics moved to the fore. Dozens of different schools contended for influence. Further, some pointed to the Soviet Union as a supposedly successful planned economy which had avoided the disasters of the capitalist world and argued for a move toward socialism. Others pointed to the success of fascism in Mussolini's Italy.
Into this tumult stepped Keynes, promising not to institute revolution but to save capitalism. He circulated a simple thesis: there were more factories and transportation networks than could be used at the current ability of individuals to pay and that the problem was on the demand side.
But many economists insisted that business confidence, not lack of demand, was the root of the problem, and that the correct course was to slash government expenditures and to cut wages to raise business confidence and willingness to hire unemployed workers. Yet others simply argued that "nature would make its course," solving the Depression automatically by "shaking out" unneeded productive capacity.
Keynes and the Classics
For Keynes the level of output and employment in the economy was determined by aggregate demand or effective demand. In a reversal of Say's Law, Keynes in essence argued that "demand creates its own supply," up to the limit set by full employment.
In "classical" economic theory—Keynes's term for the economics prior to General Theory (and specifically that of Arthur Pigou)—adjustments in prices would automatically make demand tend to the full employment level. Keynes, pointing to the sharp fall in employment and output in the early 1930s, argued that whatever the theory, this self-correcting process had not happened.
In the neo-classical theory, the two main costs are those of labor and money. If there were more labor than demand for it, wages would fall until hiring began again. If there was too much saving, and not enough consumption, then interest rates would fall until people either cut their savings rate or started borrowing.
Wages and spending
During the Great Depression, the classical theory defined economic collapse as simply a lost incentive to produce. Mass unemployment was caused only by high and rigid real wages. The proper solution was to cut wages.
To Keynes, the determination of wages is more complicated. First, he argued that it is not real butnominal wages that are set in negotiations between employers and workers, as opposed to abarter relationship. First, nominal wage cuts would be difficult to put into effect because of laws and wage contracts. Even classical economists admitted that these exist; unlike Keynes, they advocated abolishing minimum wages, unions, and long-term contracts, increasing labor-market flexibility. However, to Keynes, people will resist nominal wage reductions, even without unions, until they see other wages falling and a general fall of prices. (His prediction that mass unemployment would be necessary to deflate sterling wages back to pre-war gold values had been proven right in the 1920s).
He also argued that to boost employment, real wages had to go down: nominal wages would have to fall more than prices. However, doing so would reduce consumer demand, so that theaggregate demand for goods would drop. This would in turn reduce business sales revenues and expected profits. Investment in new plants and equipment—perhaps already discouraged by previous excesses—would then become more risky, less likely. Instead of raising business expectations, wage cuts could make matters much worse.
Further, if wages and prices were falling, people would start to expect them to fall. This could make the economy spiral downward as those who had money would simply wait as falling prices made it more valuable—rather than spending. As Irving Fisher argued in 1933, in his Debt-Deflation Theory of Great Depressions, deflation (falling prices) can make a depression deeper as falling prices and wages made pre-existing nominal debts more valuable in real terms.
Excessive saving To Keynes, excessive saving, i.e. saving beyond planned investment, was a serious problem, encouraging recession or even depression. Excessive saving results if investment falls, perhaps due to falling consumer demand, over-investment in earlier years, or pessimistic business expectations, and if saving does not immediately fall in step.
Keynes argued that saving and investment are not the main determinants of interest rates, especially in the short run. Instead, the supply of and the demand for the stock of money determine interest rates in the short run. (This is not drawn in the graph.) Neither change quickly in response to excessive saving to allow fast interest-rate adjustment.
Finally, because of fear of capital losses on assets besides money, Keynes suggested that there may be a "liquidity trap" setting a floor under which interest rates cannot fall. (In this trap, bond-holders, fearing rises in interest rates (because rates are so low), fear capital losses on their bonds and thus try to sell them to attain money (liquidity).) Even economists who reject this liquidity trap now realize that nominal interest rates cannot fall below zero (or slightly higher). In the diagram, the equilibrium suggested by the new I line and the old S line cannot be reached, so that excess saving persists. Some (such as Paul Krugman) see this latter kind of liquidity trap as prevailing in Japan in the 1990s.
Even if this "trap" does not exist, there is a fourth element to Keynes's critique (perhaps the most important part). Saving involves not spending all of one's income. It thus means insufficient demand for business output, unless it is balanced by other sources of demand, such as fixed investment. Thus, excessive saving corresponds to an unwanted accumulation of inventories, or what classical economists called a general glut. This pile-up of unsold goods and materials encourages businesses to decrease both production and employment. This in turn lowers people's incomes—and saving, causing a leftward shift in the S line in the diagram (step B). For Keynes, the fall in income did most of the job ending excessive saving and allowing the loanable funds market to attain equilibrium. Instead of interest-rate adjustment solving the problem, arecession does so. Thus in the diagram, the interest-rate change is small.
Whereas the classical economists assumed that the level of output and income was constant and given at any one time (except for short-lived deviations), Keynes saw this as the key variable that adjusted to equate saving and investment.
Finally, a recession undermines the business incentive to engage in fixed investment. With falling incomes and demand for products, the desired demand for factories and equipment (not to mention housing) will fall. This accelerator effect would shift the I line to the left again, a change not shown in the diagram above. This recreates the problem of excessive saving and encourages the recession to continue.
In sum, to Keynes there is interaction between excess supplies in different markets, asunemployment in labor markets encourages excessive saving—and vice-versa. Rather than prices adjusting to attain equilibrium, the main story is one of quantity adjustment allowing recessions and possible attainment of underemployment equilibrium.
Active fiscal policy
As noted, the classicals wanted to balance the government budget, through slashing expenditures or (more rarely) raising taxes. To Keynes, this would exacerbate the underlying problem: following either policy would raise saving (broadly defined) and thus lower the demand for both products and labor. For example, Keynesians see Herbert Hoover's June 1932 tax hike as making the Depression worse.
Keynes's ideas influenced Franklin D. Roosevelt's view that insufficient buying-power caused the Depression. During his presidency, Roosevelt adopted some aspects of Keynesian economics, especially after 1937, when, in the depths of the Depression, the United States suffered from recession yet again following fiscal contraction. Something similar to Keynesian expansionary policies had been applied earlier by both social-democratic Sweden and Nazi Germany. But to many the true success of Keynesian policy can be seen at the onset of World War II, which provided a kick to the world economy, removed uncertainty, and forced the rebuilding of destroyed capital. Keynesian ideas became almost official in social-democratic Europe after the war and in the U.S. in the 1960s.
Keynes's theory suggested that active government policy could be effective in managing the economy. Rather than seeing unbalanced government budgets as wrong, Keynes advocated what has been called countercyclical fiscal policies, that is policies which acted against the tide of thebusiness cycle: deficit spending when a nation's economy suffers from recession or when recovery is long-delayed and unemployment is persistently high—and the suppression of inflation in boom times by either increasing taxes or cutting back on government outlays. He argued that governments should solve short-term problems rather than waiting for market forces to do it, because "in the long run, we are all dead."
This contrasted with the classical and neoclassical economic analysis of fiscal policy. Fiscal stimulus (deficit spending) could actuate production. But to these schools, there was no reason to believe that this stimulation would outrun the side-effects that "crowd out" private investment: first, it would increase the demand for labor and raise wages, hurting profitability. Second, a government deficit increases the stock of government bonds, reducing their market price and encouraging highinterest rates, making it more expensive for business to finance fixed investment. Thus, efforts to stimulate the economy would be self-defeating. Worse, it would be shifting resources away from productive use by the private sector to wasteful use by the government.
The Keynesian response is that such fiscal policy is only appropriate when unemployment is persistently high, above what is now termed the Non-Accelerating Inflation Rate of Unemployment, or "NAIRU". In that case, crowding out is minimal. Further, private investment can be "crowded in": fiscal stimulus raises the market for business output, raising cash flow and profitability, spurring business optimism. To Keynes, this accelerator effect meant that government and business could be complements rather than substitutes in this situation. Second, as the stimulus occurs, gross domestic product rises, raising the amount of saving, helping to finance the increase in fixed investment. Finally, government outlays need not always be wasteful: government investment inpublic goods that will not be provided by profit-seekers will encourage the private sector's growth. That is, government spending on such things as basic research, public health, education, andinfrastructure could help the long-term growth of potential output.
Invoking public choice theory, classical and neoclassical economists doubt that the government will ever be this beneficial and suggest that its policies will typically be dominated by special interest groups, including the government bureaucracy. Thus, they use their political theory to reject Keynes' economic theory.
In Keynes' theory, there must be significant slack in the labor market before fiscal expansion is justified. Both conservative and some neoliberal economists question this assumption, unless labor unions or the government "meddle" in the free market, creating persistent supply-side orclassical unemployment. Their solution is to increase labor-market flexibility, i.e., by cutting wages, busting unions, and deregulating business.
Deficit spending is not Keynesianism. Governments had long used deficits to finance wars. But Keynesian policy is not merely spending. Rather, it is the proposition that sometimes the economyneeds active fiscal policy. Further, Keynesianism recommends counter-cyclical policies, for example raising taxes when there is abundant demand-side growth to cool the economy and to prevent inflation, even if there is a budget surplus. Classical economics, on the other hand, argues that one should cut taxes when there are budget surpluses, to return money to private hands. Because deficits grow during recessions, classicals call for cuts in outlays—or, less likely, tax hikes. On the other hand, Keynesianism encourages increased deficits during downturns. In the Keynesian view, the classical policy exacerbates the business cycle. In the classical view, of course, Keynesianism is topsy-turvy policy, almost literally fiscal madness.
"Multiplier effect" and interest rates
Two aspects of Keynes's model had implications for policy:
First, there is the "Keynesian multiplier", first developed by Richard F. Kahn in 1931. The effect on demand of any exogenous increase in spending, such as an increase in government outlays is a multiple of that increase—until potential is reached. Thus, a government could stimulate a great deal of new production with a modest outlay: if the government spends, the people who receive this money then spend most on consumption goods and save the rest. This extra spending allows businesses to hire more people and pay them, which in turn allows a further increase consumer spending. This process continues. At each step, the increase in spending is smaller than in the previous step, so that the multiplier process tapers off and allows the attainment of an equilibrium. This story is modified and moderated if we move beyond a "closed economy" and bring in the role of taxation: the rise in imports and tax payments at each step reduces the amount of induced consumer spending and the size of the multiplier effect.
Second, Keynes re-analyzed the effect of the interest rate on investment. In the classical model, the supply of funds (saving) determined the amount of fixed business investment. That is, since all savings was placed in banks, and all business investors in need of borrowed funds went to banks, the amount of savings determined the amount that was available to invest. To Keynes, the amount of investment was determined independently by long-term profit expectations and, to a lesser extent, the interest rate. The latter opens the possibility of regulating the economy through money supply changes, via monetary policy. Under conditions such as the Great Depression, Keynes argued that this approach would be relatively ineffective compared to fiscal policy. But during more "normal" times, monetary expansion can stimulate the economy, mostly by encouraging construction of new housing.
The strength of Keynesianism's influence can be seen by the wave of economists who have based their analysis on a criticism of Keynesianism.
One school began in the late 1940s with Milton Friedman. Instead of rejecting macro-measurements and macro-models of the economy, the monetarist school embraced the techniques of treating the entire economy as having a supply and demand equilibrium. However, they regarded inflation as solely being due to the variations in the money supply, rather than as being a consequence of aggregate demand. They argued that the "crowding out" effects discussed above would hobble or deprive fiscal policy of its positive effect. Instead, the focus should be onmonetary policy, which was largely ignored by early Keynesians.
Monetarism had an ideological as well as a practical appeal: monetary policy does not, at least on the surface, imply as much government intervention in the economy as other measures. The monetarist critique pushed Keynesians toward a more balanced view of monetary policy, and inspired a wave of revisions to Keynesian theory.
Another influential school of thought was based on the Lucas critique of Keynesian economics. This called for greater consistency with microeconomic theory and rationality, and particularly emphasized the idea of rational expectations. Lucas and others argued that Keynesian economics required remarkably foolish and short-sighted behavior from people, which totally contradicted the economic understanding of their behavior at a micro level. New classical economics introduced a set of macroeconomic theories which were based on optimising microeconomic behavior, for instance real business cycles.
Keynesian ideas were criticized by free market economist and philosopher Friedrich Hayek. Hayek's most famous work The Road to Serfdom, was written in 1944. Hayek taught at the London School of Economics from 1931 to 1950. Hayek criticized Keynesian economic policies for what he called their fundamentally collectivist approach, arguing that such theories, no matter their presumptively utilitarian intentions, require centralized planning, which Hayek argued leads to totalitarian abuses. Keynes seems to have been aware of the potential pitfalls of his economy theory, since, in the foreword to the German version of the 'The General Theory of Employment Interest and Money', he declared that "the theory of aggregated production, which is the point of ['The General Theory of Employment Interest and Money'], nevertheless can be much easier adapted to the conditions of a totalitarian state [eines totalen Staates] than the theory of production and distribution of a given production put forth under conditions of free competition and a large degree of laissez-faire." 
Another criticism leveled by Hayek against Keynes was that the study of the economy by the relations between aggregates is fallacious, and that recessions are caused by micro-economic factors. Hayek claimed that what start as temporary governmental fixes usually become permanent and expanding government programs, which stifle the private sector and civil society. Keynes himself described the critique as "deeply moving", which was quoted on the cover of the Road to Serfdom.
James Buchanan followed the criticism by noting that, since Keynes had roots in the classically liberal or free market economic tradition, he was more concerned with what was good policy, not on how it would be executed. In the book Democracy in Deficit, he notes that Keynes never thought out how, say, deficit spending would give a blank check to politicians to run deficits even when orthodox Keynesian analysis didn't find it proper.