Toto: New encyclopedia article: Aggregate Supply

2026-10-06T04:43:59Z

New encyclopedia article: Aggregate Supply

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'''Aggregate supply''' ('''AS''') is the total quantity of goods and services that firms in an economy are willing and able to produce at a given overall price level during a specified period. Together with [[Aggregate Demand|aggregate demand]], it determines the equilibrium level of output and prices in the macroeconomy. The behaviour of aggregate supply is central to understanding the trade-off between output and inflation, and to the design of macroeconomic stabilisation policy.

== Definition ==

Aggregate supply represents the productive capacity of an economy and the willingness of firms to utilise that capacity at different price levels. Unlike the supply curve for a single good, the aggregate supply curve reflects the combined production decisions of all firms in the economy, and its shape depends critically on the time horizon under consideration and on the degree of flexibility in prices and wages.

Economists distinguish between the '''short-run aggregate supply''' (SRAS) curve and the '''long-run aggregate supply''' (LRAS) curve. The difference between them arises from the speed with which prices and wages adjust to changes in economic conditions.

== The short-run aggregate supply curve ==

In the short run, some prices and wages are sticky or slow to adjust. Under these conditions, the short-run aggregate supply curve slopes upward: a higher price level induces firms to increase production. The intuition is that firms whose output prices adjust more quickly than their input costs will find production more profitable when prices rise, leading them to expand output and employment.

The upward slope of the short-run aggregate supply curve can be explained by several mechanisms. '''Sticky wages''' arise from long-term labour contracts and social norms, so that nominal wages do not immediately rise with prices. '''Sticky prices''' occur because firms face menu costs—the cost of changing prices—and prefer to avoid frequent adjustments. '''Misperceptions''' about changes in relative versus absolute prices may also lead firms to respond to price increases by raising output.

The steepness of the short-run aggregate supply curve matters greatly for policy. When the curve is relatively flat, increases in aggregate demand raise output substantially with little effect on prices. When the curve is steep—as it becomes as the economy approaches full capacity—increases in demand mostly raise prices rather than output.

== The long-run aggregate supply curve ==

In the long run, all prices and wages are flexible, and output is determined by the economy's productive resources and technology rather than by the price level. The long-run aggregate supply curve is therefore '''vertical''' at the level of potential output (also called full-employment output). Changes in the price level do not affect long-run output; only changes in the factors of production or in technology can shift the long-run aggregate supply curve.

Potential output depends on the quantity and quality of labour, the stock of capital, the state of technology, and the efficiency with which these resources are combined—that is, on [[Total Factor Productivity|total factor productivity]]. Growth in potential output over time is the source of long-run growth in living standards.

== Shifts in aggregate supply ==

The aggregate supply curve—both short-run and long-run—can shift in response to various factors.

A '''shift to the right''' (an increase in aggregate supply) can result from improvements in productivity, reductions in input prices, technological innovation, increases in the labour force or capital stock, or policies that improve the flexibility of markets.

A '''shift to the left''' (a decrease in aggregate supply) can result from increases in input prices—most notably oil and energy prices—natural disasters, increases in taxes on production, or adverse regulatory changes. A leftward shift in short-run aggregate supply raises both prices and reduces output, a combination known as '''[[Stagflation|stagflation]]''', which poses a difficult challenge for policymakers because the usual tools for fighting inflation and unemployment pull in opposite directions.

== The aggregate supply and demand model ==

The interaction of aggregate demand and aggregate supply determines the economy's equilibrium. In the short run, a shift in either curve changes both output and the price level. In the long run, output returns to potential, and demand shifts affect only the price level. This framework provides the basis for analysing the effects of demand shocks, which are disturbances originating in aggregate demand, and supply shocks, which are disturbances originating in aggregate supply.

A '''demand shock''', such as a surge in consumer spending or a burst of fiscal stimulus, shifts aggregate demand and moves the economy along the short-run aggregate supply curve, raising output and prices in the short run. If the shock persists, wages and prices eventually adjust, returning output to potential while leaving the price level permanently higher.

A '''supply shock''', such as a sharp increase in oil prices, shifts short-run aggregate supply leftward, raising prices and reducing output simultaneously. Because supply shocks worsen both inflation and unemployment, they present a particularly difficult policy dilemma.

== Policy implications ==

The aggregate supply and demand framework has important implications for policy. Demand management policies—fiscal and monetary measures aimed at influencing aggregate demand—can stabilise output and employment in the short run, but they cannot raise long-run output, which is governed by supply-side factors.

Policies that improve the productive capacity of the economy—investment in education, infrastructure, and technology; reductions in regulatory burdens; and measures that improve labour market flexibility—shift the long-run aggregate supply curve to the right, raising potential output and living standards without generating inflation. The distinction between demand management and supply-side policy is central to contemporary macroeconomic debate.

== See also ==

* [[Aggregate Demand]]
* [[Stagflation]]
* [[Supply Shock]]
* [[Total Factor Productivity]]
* [[Fiscal Policy]]

== References ==

<ref name="r1">International Monetary Fund, ''Finance and Development'' series on macroeconomic concepts.</ref>
<ref name="r2">OECD, ''Economic Outlook'' methodology annexes.</ref>
<ref name="r3">Bank of England, ''Quarterly Bulletin'' on supply-side analysis.</ref>

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Aggregate Supply - Revision history

Toto: New encyclopedia article: Aggregate Supply