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Multiplier (economics)
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In economics, a '''multiplier''' effect – or, more completely, the spending/income multiplier effect – occurs when a change in spending causes a disproportionate change in
aggregate demand. It is particularly associated with
Keynesian economics; some other schools of economic thought reject or downplay the importance of multiplier effects, particularly in the long run.
The '''local multiplier effect''' specifically refers to the effect that spending has when it is circulated through a local economy. For example, when the building of a sports stadium is proposed, one of the suggested benefits is that it will raise income in the area by more than the amount spent on the project.
Overview
Image:simpmult.PNG frame|200px|right| fig. 1 - The Simple Multiplier Process.
The basic assumption of the multiplier effect is that the economy starts off with unused resources, for example, that many workers are
unemployment_types#Cyclical_unemployment cyclically unemployed and much of industrial capacity is sitting idle or incompletely utilized. By increasing demand in the economy it is then possible to boost production. If the economy was already at
full employment, with only structural, frictional, or other supply-side types of unemployment, any attempt to boost demand would only lead to
inflation. For various ''
laissez-faire'' schools of economics which embrace
Say's Law and deny the possibility of
inefficiency Keynesian inefficiency and under-employment of resources, therefore, the multiplier concept is irrelevant or wrong-headed.
Ass an example, consider the government increasing its expenditure on roads by $1 million, without a corresponding increase in taxation. This sum would go to the road builders, who would hire more workers and distribute the money as wages and profits. The households receiving these incomes will save part of the money and spend the rest on consumer goods. These expenditures in turn will generate more jobs, wages, and profits, and so on with the income and spending circulating around the economy.
The multiplier effect arises because of the ''induced'' increases in consumer spending which occur due to the increased incomes -- and because of the ''feedback'' into increasing business revenues, jobs, and income again. This process does not lead to an economic explosion not only because of the supply-side barriers at
potential output (full employment) but because at each "round", the increase in consumer spending is less than the increase in consumer incomes. That is, the
marginal propensity to consume ('''mpc''') is less than one, so that each round some extra income goes into
saving, leaking out of the cumulative process. Each increase in spending is thus smaller than that of the previous round, preventing an explosion.
Details
Here, the marginal propensity to consume equals:
:: '''mpc''' = Δ'''C'''/Δ'''Y'''
where '''C''' is consumer spending and '''Y''' is consumer disposable income.
If the multiplier process is going LL
downward, as in a
recession, the fall in demand creates its own unused resources, so that the basic assumption of the theory applies.
The eventual amount by which output expands is governed by the
marginal propensity to save, which is the proportion of extra income that is saved rather than consumed. If the marginal propensity to save is large, less money is returned into the economy with each circulation so the multiplier effect is smaller. The value of the multiplier in a
closed economy with no taxes is given by
:: '''mult''' = 1/(1 – '''mpc''') = 1/'''s'''
where '''s''' is the
marginal propensity to save, i.e., the increase in consumer
saving divided by the increase in consumer
disposable income. In the
Keynesian economics Keynesian model, '''s''' equals one ''minus'' the '''mpc'''. (Note that '''s''' cannot equal zero, nor can the '''mpc''' equal one.)
In this simple model, the multiplier can be used to predict changes in GDP ('''Y''') for a given change in spending, '''X'''.
:: predicted Δ'''Y''' = '''mult''' * Δ'''X'''
Of course, the validity of this equation depends of the validity of the assumptions of the model.
This is also true of the formula for the multiplier. Taxes and imports tend to reduce the value of the multiplier ("leakage"). With these, the spending/income multiplier process is more complex, as seen in figure 2, above.
:: '''mult''' = 1/'''mlr'''
This formula of the multiplier is obtained when we take into account the effects of all leakages, which combine into the 'Marginal Leakage Rate' ('''mlr''') from the
circular flow. (Again, '''mlr''' cannot equal zero.)
The value of the multiplier is also lower, less than 1/'''s''', since some of the demand stimulus or restraint ''leaks out'' to affect imports from the rest of the world and tax revenues. This weakening occurs because imports do not lead automatically to spending on the country's exports and increased tax revenues do not automatically cause increased government spending. Though this reduces the value of '''mult''', it does not undermine the validity of the third equation above.
Category:Keynesian economics
Category:Economics effects
de:Multiplikator (Volkswirtschaft)
ja:乗数効果
pl:Mnożnik (ekonomia)
ro:Multiplicator (economie)
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