Aggregate Demand vs Aggregate Supply
Aggregate Demand and Aggregate Supply are two Aggregate Demand & Supply concepts in AP Economics that students often mix up. Aggregate demand is the total demand for final goods and services in an economy at a given time. Aggregate supply is the total supply of final goods and services in an economy at a given time. Here is how they compare side by side.
Aggregate demand is the sum of consumption, investment, government spending, and net exports. It represents the total amount of goods and services that households, businesses, the government, and foreigners plan to buy at a given level of income.
Aggregate supply represents the total amount of goods and services that firms plan to produce and sell at a given price level. In the short run, aggregate supply can increase or decrease with changes in the price level. In the long run, aggregate supply is determined by an economy's factors of production.
Aggregate Demand vs Aggregate Supply: The Two Sides of the Macro Market
| Aggregate demand | Aggregate supply | |
|---|---|---|
| What it shows | Total spending on domestic output at each price level | Total output firms produce at each price level |
| Slope | Downward | Upward in the short run, vertical in the long run |
| Components or determinants | Consumption, investment, government spending, net exports | Input prices, productivity, resources, technology, expectations |
| Why it slopes that way | The wealth, interest rate, and exchange rate effects | Sticky input prices in the short run, none of which bind in the long run |
| A rightward shift causes | Higher price level and higher output | Lower price level and higher output |
| Vertical version exists | No | Yes, long-run aggregate supply at full-employment output |
Why aggregate demand slopes down for reasons the micro curve does not
A single market's demand curve slopes down largely because of substitution: when beef gets expensive you buy chicken. That cannot explain aggregate demand, because when the whole price level rises there is nothing domestic to substitute into. Three different effects do the work. The wealth effect: a higher price level makes the money people hold worth less, so they spend less. The interest rate effect: a higher price level increases money demand, which raises interest rates, which reduces investment and interest-sensitive consumption. The exchange rate effect: a higher domestic price level makes exports less competitive and imports more attractive, so net exports fall. Naming these three specifically is a common rubric row, and answering with substitution earns nothing.
A shift in one is not a movement along the other
The single most costly error on this topic is confusing a shift with a movement. A change in the price level moves you ALONG both curves and shifts neither. Anything else, a tax change, a spending change, a shift in expectations, a change in input prices, shifts one of them. Concretely: a rise in oil prices shifts short-run aggregate supply left; it does not shift aggregate demand even though it raises the price level. A cut in household income taxes shifts aggregate demand right; it does not shift aggregate supply even though it raises output. Ask who writes the check before you decide which curve moves: a tax paid by households works through disposable income and consumption, so it lands on aggregate demand, while a per-unit tax or subsidy on firms changes the cost of producing each unit and therefore shifts short-run aggregate supply. Draw the new curve and mark the new equilibrium every time rather than describing the change in words. Set both up at /sandbox/adas.
Where the long run sits, and why it matters
Long-run aggregate supply is vertical at full-employment output, because in the long run all input prices adjust and the economy produces what its resources and technology permit regardless of the price level. Only the things that change productive capacity shift it: more workers, more capital, better technology, better institutions. Short-run aggregate supply slopes up because some input prices, wages in particular, are sticky, so a higher output price raises profit margins and firms produce more. Every AD-AS question ultimately asks where the short-run equilibrium sits relative to that vertical line, because that is what defines a recessionary or inflationary gap. See /glossary/compare/recessionary-gap-vs-inflationary-gap.
Frequently asked questions
What is the difference between aggregate demand and aggregate supply?
Aggregate demand shows the total quantity of domestic output buyers want at each price level, made up of consumption, investment, government spending, and net exports. Aggregate supply shows the total quantity firms produce at each price level. They intersect at the economy's short-run equilibrium price level and real GDP.
Why does the aggregate demand curve slope downward?
Because of three effects: the wealth effect, where a higher price level reduces the real value of money holdings and so reduces spending; the interest rate effect, where a higher price level raises money demand and interest rates and so reduces investment; and the exchange rate effect, where a higher domestic price level reduces net exports. What does not apply is substitution between one domestic good and another, because every domestic price rises at once. Substitution toward foreign goods still applies, and that is the exchange rate effect.
What shifts aggregate demand versus aggregate supply?
Aggregate demand shifts when consumption, investment, government spending, or net exports change for reasons other than the price level, so tax changes, confidence, interest rates, and foreign income all shift it. Short-run aggregate supply shifts when input prices, productivity, resource availability, or expectations change. A change in the price level itself shifts neither; it moves you along both.
Live AD/AS Model graph. Drag the curves, or open the full version.
Related comparisons
Get AP Econ exam tips in your inbox
Occasional emails with study tips, new interactive graphs, and exam-season reminders. Free, no spam.
No spam. Unsubscribe anytime. Read our privacy policy.
Keep track of what you have studied
A free EconLearn account adds progress tracking, your quiz history, and achievements. Studying here is free either way, and there is nothing to pay for as a student.
Create a free accountAlready have one? Sign in
Last updated