Supply shocks vs demand shocks: how each moves output and prices

A demand shock is a change that shifts the aggregate demand curve, so total planned spending is higher or lower at every price level. A supply shock is a change that shifts the short run aggregate supply curve, so firms produce more or less real GDP at every price level. The two shocks leave different fingerprints. A demand slump cuts both output and the price level. An adverse supply shock cuts output while raising the price level, which is the pattern textbooks call stagflation.

This page is for AP Macroeconomics and intro economics study. It is educational only and is not investment, financial, tax, or legal advice. It makes no forecast about the current economy. The numbers in the worked example are invented for practice.

The AD AS picture both shocks use

OpenStax builds the aggregate demand and aggregate supply model so that the horizontal axis is real GDP and the vertical axis is the price level, meaning an index of average prices such as the GDP deflator. Aggregate supply is the total quantity of real GDP firms will produce and sell. The short run aggregate supply curve slopes up because, with input prices held fixed, a higher price level for final goods raises profits and encourages more production. The vertical line at potential GDP is long run aggregate supply: the amount of real GDP the economy can produce by fully employing its existing labour, physical capital, and technology.

Aggregate demand is total planned spending on domestic goods and services. OpenStax writes it as consumption plus investment plus government spending plus exports minus imports. The aggregate demand curve slopes down because a higher price level reduces spending through the wealth effect, the interest rate effect, and the foreign price effect. Equilibrium is the intersection of aggregate demand and short run aggregate supply. That point sets both real GDP and the price level together.

OpenStax also warns that this graph is not the same as ordinary market supply and demand. The vertical axis is a price index for the whole economy, not the price of one good relative to another. The horizontal axis is total real GDP, not the quantity in one market. A full walkthrough of the slopes and of recessionary and inflationary gaps is on the aggregate demand and aggregate supply page.

What counts as a demand shock

A demand shock changes spending at every price level, which shifts the aggregate demand curve. OpenStax groups the usual causes into changes in household or firm behaviour and changes in government tax or spending policy.

Higher consumer or business confidence raises consumption or investment and shifts aggregate demand right. Lower confidence does the reverse.
Higher government spending shifts aggregate demand right. Lower government spending shifts it left.
Tax cuts that raise consumption or investment shift aggregate demand right. Tax increases shift it left.
OpenStax also notes that monetary policy can shift aggregate demand by changing interest rates and credit. Lower interest rates tend to raise household spending on large purchases and business investment.

When aggregate demand shifts right, the new equilibrium has a higher real GDP and a higher price level. When aggregate demand shifts left, the new equilibrium has a lower real GDP and a lower price level. How large those moves are depends on whether the economy is on the flatter or the steeper part of short run aggregate supply.

OpenStax, looking back at Say's law and Keynes' law, says both sides matter. Keynes' law, that demand creates its own supply, is a better description of a few months to a few years, when firms may produce below their potential because spending is weak. Say's law, that supply creates its own demand, is a better description over years or decades, when the economy's capacity to produce sets the pace. The AD AS graph is the classroom tool that holds both ideas at once.

What counts as a supply shock

A supply shock changes how much firms will produce at every price level, which shifts short run aggregate supply. OpenStax highlights two main drivers: productivity and input prices.

Higher productivity lets the same workers produce more output, so short run aggregate supply shifts right. Potential GDP, and therefore long run aggregate supply, shifts right as well.
Higher prices for widely used inputs such as energy or labour shift short run aggregate supply left, because production is less profitable at any given price level for final goods. Lower input prices shift it right. Unlike productivity, a change in input prices does not generally move long run aggregate supply.
OpenStax also describes sudden disruptions to inputs or labour, such as a freeze that destroys crops, as leftward shifts of aggregate supply.

A rightward shift of short run aggregate supply, with aggregate demand unchanged, raises real GDP and puts downward pressure on the price level. A leftward shift does the opposite: real GDP falls and the price level rises. OpenStax calls that combination of weaker output, higher unemployment, and a higher price level stagflation. The stagflation explainer takes that case further.

One sketch, two fingerprints

The diagram below is a teaching sketch, not real data. The left panel shows a demand slump. The right panel shows an adverse supply shock. Both start from the same original equilibrium E0.

Teaching sketch: a left shift of aggregate demand lowers both the price level and real GDP. A left shift of short run aggregate supply raises the price level and lowers real GDP. Not drawn to scale.

Demand slump (left). Aggregate demand moves from AD0 to AD1. The economy slides down short run aggregate supply to E1. Real GDP is lower and the price level is lower. If the fall in activity is significant and widespread, it can be part of a recession and a wider business cycle downturn. The output gap usually turns more negative.
Adverse supply shock (right). Short run aggregate supply moves from SRAS0 to SRAS1. The economy moves up the unchanged aggregate demand curve to a higher price level and a lower real GDP. That is why an energy or labour cost jump is not only a demand story: the first curve that moves is short run aggregate supply.

A favourable supply shock, such as a productivity gain or cheaper widely used inputs, does the reverse of the right panel: output rises and the price level comes under downward pressure. A demand boom does the reverse of the left panel: both output and the price level rise.

A quick checker

Choose the best description. These are classroom cases, not forecasts.

Case 1. Households feel less confident and spend less at every price level.

Case 2. A widely used input becomes more expensive, so firms produce less at every price level.

Case 3. The price level rises and people buy fewer goods, while confidence, policy, and input prices are unchanged.

Worked example (hypothetical numbers)

The figures below are invented for practice. They are not real data for any country.

Situation	Price level	Real GDP index
Original equilibrium	100	200
After a demand slump	94	188
After an adverse supply shock	108	186

Read the original point. At a price level of 100, real GDP is 200. That is where aggregate demand and short run aggregate supply first meet.
Demand slump. Spending falls at every price level, so aggregate demand shifts left. The new point has a price level of 94 and a real GDP index of 188. Both the price level and output are lower than before. The output gap is more negative if potential output is still 200.
Adverse supply shock, from the same start. Firms produce less at every price level, so short run aggregate supply shifts left. The new point has a price level of 108 and a real GDP index of 186. Output is lower, but the price level is higher. That is the stagflation fingerprint.
Do not treat the two rows as one story. The demand slump and the supply shock are separate classroom cases. They are not a sequence of dates, and they are not a forecast.

The College Board lists Unit 3 of AP Macroeconomics as National Income and Price Determination, with an exam weighting of 17 to 27 percent of the multiple choice section on its AP Central course page (retrieved 8 Nov 2026). Drawing which curve moved, and in which direction prices and output went, is a core skill for that unit. The AP Macroeconomics study hub maps each unit to explainers.

How this fits the rest of the course

The same AD AS graph is how the course talks about gaps, inflation pressure, and many policy moves. A demand slump that opens a negative output gap is one way a business cycle contraction can appear. An adverse supply shock can raise inflation even while output weakens, which is why the Phillips curve short run trade off is not a simple rule in every episode. Policy that aims at spending works through aggregate demand. Productivity and input costs work through aggregate supply. For the inflation measures themselves, start with the inflation topic hub. For the output side, start with the GDP topic hub.

Common exam mistakes

Drawing a movement along a curve when the story is a shift. A change in the price level alone slides the economy along aggregate demand or short run aggregate supply. A shock changes spending or production at every price level, so the whole curve moves.
Treating an oil or energy price jump as only a demand story. Energy is a widely used input. OpenStax treats a rise in such input prices as a left shift of short run aggregate supply. Households may later change spending, but that is a second step, not the first curve that moves.
Forgetting that an adverse supply shock can raise the price level while cutting output. Students sometimes assume prices and output always move together. That is true for demand shocks and false for supply shocks.
Shifting long run aggregate supply every time input prices change. OpenStax notes that input price changes generally move short run aggregate supply only. Productivity changes can move both short run and long run aggregate supply.
Using the micro supply and demand graph in place of AD AS. Label the axes as the price level and real GDP, not as the price and quantity of one good.

Sources

Frequently asked questions

What is the difference between a supply shock and a demand shock?

A demand shock shifts the aggregate demand curve, so total planned spending changes at every price level. A supply shock shifts the short run aggregate supply curve, so firms change how much real GDP they produce at every price level. The two shifts leave different marks on output and prices.

Why can an adverse supply shock raise prices while cutting output?

When a widely used input becomes more expensive, short run aggregate supply shifts left. The new intersection with aggregate demand is at a lower real GDP and a higher price level. OpenStax describes that mix of weaker output and a higher price level as stagflation.

What happens to prices and output after a demand slump?

A fall in consumption, investment, government spending, or net exports shifts aggregate demand left. The new equilibrium has both a lower real GDP and a lower price level. That is the opposite price move from an adverse supply shock.

Is a change in the price level itself a shift of aggregate demand?

No. A higher or lower price level moves the economy along the aggregate demand curve because of the wealth effect, the interest rate effect, and the foreign price effect. A shift requires a change in spending at every price level, such as a change in confidence, government spending, or taxes.