AP Macroeconomics: Aggregate Supply (SRAS vs LRAS) – Shifters, Sticky Wages, Stagflation

AP Macroeconomics – Aggregate Supply (SRAS vs LRAS) – Shifters, Sticky Wages, Stagflation

## What This Is
Aggregate Supply (AS) shows the total quantity of goods and services that firms are willing and able to produce at each price level. The short?run AS curve (SR?AS) is upward?sloping because some input prices (especially wages) are “sticky,” while the long?run AS curve (LR?AS) is vertical at potential GDP. Understanding the shifters of SR?AS and LR?AS, why wages can be sticky, and how stagflation (simultaneous high inflation?+?high unemployment) appears on the AD?AS model is a staple of the AP?Macroeconomics exam.

Real?world hook: In 2022 the U.S. experienced a sharp rise in gasoline prices (inflation) while the unemployment rate stayed near 3?%—a classic stagflation episode that forces students to trace SR?AS leftward shifts caused by higher oil?producer costs.

## Key Terms & Formulas

• SR?AS (Short?Run Aggregate Supply) curve – Upward?sloping; vertical axis = Price level (P), horizontal axis = Real GDP (Y). Shows output when at least one input price (usually wages) is fixed in the short run.
• LR?AS (Long?Run Aggregate Supply) curve – Vertical at Potential GDP (Y*); reflects that in the long run all input prices adjust, so output depends only on resources and technology.
• Sticky Wages – The tendency of nominal wages to adjust slowly to changes in the price level, causing SR?AS to be upward?sloping.
• Cost?Push Inflation – Inflation caused by an increase in production costs (e.g., higher oil prices) that shifts SR?AS left.
• Demand?Pull Inflation – Inflation caused by an increase in aggregate demand (AD) that shifts the AD curve right.
• Stagflation – A macroeconomic condition where SR?AS shifts left (higher costs) while AD remains unchanged or falls, producing higher price level and lower real GDP.
• AD?AS Model – Graph with AD (downward?sloping), SR?AS (upward?sloping), LR?AS (vertical). Intersection = equilibrium price level and output.
• Real GDP Gap = Potential GDP – Actual GDP – Positive gap = recessionary gap; negative gap = inflationary gap.
• Phillips Curve (SR) – Inverse relationship between inflation and unemployment; useful for explaining why sticky wages can cause a trade?off in the short run.
• Formula: Real GDP = Nominal GDP / (Price Level / 100) – Converts nominal dollars into real output; essential when discussing shifts caused by price?level changes.

## Step?by?Step / Process Flow

1. Draw the baseline AD?AS diagram – Plot AD (downward), SR?AS (upward), and LR?AS (vertical at Y*). Mark the initial equilibrium (E?).
2. Identify the shock – e.g., a sudden rise in oil prices-a cost?push shock.
3. Shift the SR?AS curve left – Keep AD unchanged (or shift AD left if consumer confidence also falls). Label the new SR?AS as SR?AS?.
4. Find the new short?run equilibrium – Intersection of AD and SR?AS? gives a higher price level (P?) and lower output (Y?). Note the recessionary gap (Y*?–?Y?).
5. Explain the role of sticky wages – Because wages do not instantly rise with P?, firms still face higher input costs, keeping SR?AS left?shifted.
6. Project the long?run adjustment – Over time, wages and other input prices rise, shifting SR?AS back right toward LR?AS, restoring Y* but at a higher price level (P?).

## Common Mistakes

• Mistake: Saying “SR?AS shifts right when the price level rises.”
  Correction: A change in the price level causes a movement along the SR?AS curve; only a change in input costs (e.g., wages, oil) shifts the curve.

• Mistake: Confusing “sticky wages” with “sticky prices.”
  Correction: Sticky wages refer to slow adjustment of nominal wages; sticky prices refer to slow adjustment of overall price level. Both create short?run upward?sloping SR?AS, but they are distinct concepts.

• Mistake: Treating stagflation as a demand?side problem.
  Correction: Stagflation originates from a leftward SR?AS shift (cost?push), not from AD. The AD curve may stay the same or even shift left, but the key driver is higher production costs.

• Mistake: Believing LR?AS can shift left or right due to monetary policy.
  Correction: LR?AS moves only with changes in resources, technology, or institutional factors (e.g., labor force growth). Monetary or fiscal policy shifts AD, not LR?AS.

• Mistake: Using the Phillips Curve to claim “higher inflation always lowers unemployment.”
  Correction: The short?run Phillips Curve shows a trade?off, but in the long run the curve is vertical—no stable trade?off exists.

## AP Exam Insights

1. Graphing Requirement: FRQs often ask you to draw an AD?AS diagram, label the curves, and show the effect of a specific shock (e.g., “oil price shock”). Remember to label the initial and new equilibria and indicate the direction of the shift.
2. Distinguish Shifters vs. Movements: Multiple?choice items test whether you recognize that a change in the price level moves along SR?AS, while a change in input costs shifts SR?AS.
3. Stagflation Prompt: A typical FRQ will give a scenario of rising inflation and rising unemployment; you must identify it as stagflation, explain the leftward SR?AS shift, and discuss short?run vs. long?run outcomes.
4. Policy Evaluation: The exam may ask which policy (expansionary fiscal vs. monetary) is most effective for closing a recessionary gap caused by a leftward SR?AS shift—answer: supply?side policies (e.g., tax cuts on production) are needed, not demand?side stimulus alone.

## Quick Check Questions

1. MC: A sudden increase in the minimum wage is most likely to cause which of the following?
2. A) SR?AS shift right
3. B) SR?AS shift left
4. C) AD shift right

5. D) LR?AS shift left
   Answer: B. A higher minimum wage raises labor costs, shifting SR?AS left (higher price level, lower output).

6. FRQ?style: “The economy is experiencing rising inflation and rising unemployment. Explain why this situation is called stagflation and illustrate it on an AD?AS graph.”
   Answer: Stagflation occurs when SR?AS shifts left due to higher production costs (e.g., oil price shock). On the graph, SR?AS moves left, raising the price level and lowering real GDP, while AD stays unchanged.

7. MC: In the long run, an economy’s LR?AS curve is vertical because:

8. A) Prices are sticky.
9. B) All input prices fully adjust.
10. C) Government spending is fixed.
11. D) Money supply is constant.
    Answer: B. When all input prices adjust, output depends only on resources and technology, making LR?AS vertical.

## Last?Minute Cram Sheet

1. SR?AS = upward?sloping; LR?AS = vertical at potential GDP (Y*).
2. Sticky wages-SR?AS left shift when input costs rise.
3. Cost?push inflation = leftward SR?AS shift; demand?pull inflation = rightward AD shift.
4. Stagflation = leftward SR?AS shift + (often) unchanged AD-higher P & lower Y.
5. Price?level change-movement along SR?AS; only input?price change shifts SR?AS.
6. LR?AS moves only with changes in resources, technology, or institutional factors.
7. Real GDP gap = Y* – Y; positive gap = recessionary, negative gap = inflationary.
8. Phillips Curve (SR) shows inverse inflation?unemployment; long?run curve is vertical.
9. Supply?side policies (e.g., tax cuts on firms) are needed to shift SR?AS right.
10. When drawing AD?AS, label axes: Price Level (vertical) vs. Real GDP (horizontal).

Good luck—master these curves, shifters, and the stagflation story, and you’ll be ready for any AP?Macroeconomics question on Aggregate Supply!