Macroeconomics
Aggregate Supply
Total goods and services produced — short-run vs long-run views differ
Aggregate supply (AS) is total quantity of goods and services produced in economy at given price level. Two key views. (1) Short-run AS: upward-sloping; firms produce more at higher prices (sticky wages). Output above potential possible briefly. (2) Long-run AS: vertical at potential output; output determined by productive capacity, not price level. Together with aggregate demand: explains output, inflation, business cycles. Shifts: changes in productivity, technology, labor force, capital, energy prices. Long-run growth: from rightward shifts of long-run AS. Foundation of macroeconomic analysis.
- DefinitionTotal goods/services produced at given price level
- Short-run ASUpward-sloping; firms produce more at higher prices
- Long-run ASVertical at potential output
- DeterminantsProductivity, labor, capital, technology, resources
- Long-run growthRightward shift of long-run AS
- StagflationNegative supply shock + inflation
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Why AS matters
- Macroeconomic analysis. Foundation.
- Long-run growth. Productive capacity.
- Inflation analysis. Demand vs supply.
- Supply shocks. Stagflation diagnosis.
- Public policy. Targeting structural growth.
- International comparisons. Productivity differences.
- Education. Foundational macro.
Common misconceptions
- Always upward-sloping. Long-run vertical.
- Demand can grow output long-run. Only AS can.
- Easy to measure. Potential output uncertain.
- Same in all economies. Different supply structures.
- Stable. Constantly evolving.
- Just for goods. Includes services.
Frequently asked questions
What's aggregate supply?
Total quantity of all goods and services produced in economy at any given price level. Two perspectives. Short-run: how much firms supply given current capacity, prices, wages. Long-run: economy's productive capacity (potential output). Different shapes: short-run upward sloping, long-run vertical. Together with AD: macro model.
Why is short-run AS upward-sloping?
At higher prices, firms more profitable; produce more. (1) Sticky wages: wages don't adjust instantly to inflation; profit margins increase. (2) Sticky prices: some firms slow to change prices; less output adjustment. (3) Misperceptions: firms think price rises are real (relative price changes), produce more. Result: higher prices → more production. Slope steeper as economy approaches capacity.
Why is long-run AS vertical?
At potential output. Determined by: labor force, capital stock, technology, natural resources. Independent of price level — in long run. Higher prices: just inflation; doesn't increase real output. Once wages, expectations adjust: same real output. So vertical at potential GDP. Long-run AS shifts: only with productivity, capital, etc. changes.
What shifts long-run AS?
Real factors. (1) Labor force: more workers, more skills. (2) Capital: more investment in machines, factories. (3) Technology: better productivity. (4) Natural resources. (5) Education and human capital. (6) Institutions: property rights, rule of law. Long-run growth: from these factors. Cannot grow long-run via demand alone.
What's a supply shock?
Sudden change in costs of inputs. Negative shock: oil prices spike, supply chain disruption. Reduces short-run AS (more expensive to produce). Result: prices rise, output falls (stagflation). Examples: 1970s oil crises, 2020 COVID supply chain disruptions, 2022 Ukraine war energy shocks. Different from demand shocks.
What's stagflation?
Combination: stagnant economy + inflation. Caused by negative supply shocks. Traditional Phillips curve: inflation and unemployment trade off. Stagflation: both up. Requires supply-side cause. 1970s: oil shocks caused. Difficult: monetary policy can fight one but not both. Recent debates: was 2021-2023 stagflation? (Mostly demand-driven, not classic stagflation.)
How is potential output measured?
Output economy could produce at full employment. Estimated from: long-term trend of GDP, productivity studies, demographics. Output gap: difference between actual and potential. Negative gap: economy underperforming. Positive gap: overheating. Hard to measure precisely. Still useful for: policy guidance, recession identification.