AP Macroeconomics

## Learning Outcomes

- Distinguish between **demand-pull inflation** and **cost-push inflation**
- Explain how each type of inflation appears on an AD–AS graph
- Identify common causes of an **AD right shift** and an **SRAS left shift**
- Predict the short-run effects on **price level**, **real GDP**, and **unemployment**
- Explain why **stagflation** is linked to supply-side problems rather than rising aggregate demand
- Apply this topic to multiple-choice and free-response AP Macroeconomics questions

## AP Macroeconomics Syllabus

For the AP Macroeconomics, you are expected to understand short-run inflation in the AD–AS model, with a focus on the following syllabus points:

- Know that **demand-pull inflation** is caused by an increase in **aggregate demand**
- Know that **cost-push inflation** is caused by a decrease in **short-run aggregate supply**
- Identify that an **AD right shift** raises the **price level** and **real GDP** in the short run
- Identify that an **SRAS left shift** raises the **price level** but lowers **real GDP** in the short run
- Explain why higher consumer spending, investment, government spending, or net exports can create demand-pull inflation
- Explain why higher nominal wages, energy costs, raw material costs, or negative supply shocks can create cost-push inflation
- Understand that **stagflation** means rising price level with falling output and higher unemployment
- Draw and interpret AD–AS graphs using correctly labeled **AD**, **SRAS**, **LRAS**, **price level**, and **real GDP**

## Test Your Knowledge

_Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, look more closely at that area during your revision._

1. What graph shift causes demand-pull inflation in the short run?
2. How does cost-push inflation affect real GDP differently from demand-pull inflation?
3. Why is stagflation associated with a leftward shift of SRAS rather than a rightward shift of AD?
4. Name two causes of an increase in aggregate demand.
5. Name two causes of a decrease in short-run aggregate supply.

## Introduction

Inflation in AP Macroeconomics is not just “prices rising.” On the exam, you are usually asked to explain **why** the price level rises and what happens to **real GDP** at the same time. That is the key distinction. The same symptom, a higher price level, can come from either stronger demand or weaker short-run supply.

This is why the AD–AS model matters so much. If aggregate demand increases, the economy moves to a new short-run equilibrium with higher output and a higher price level. If short-run aggregate supply decreases, the economy also gets a higher price level, but output falls instead. That output difference is one of the most tested ideas in Unit 3.

> **Key Term: inflation**
> A sustained increase in the overall price level in the economy.

### Demand-pull inflation: inflation caused by rising aggregate demand

**Demand-pull inflation** happens when total spending in the economy rises, so firms face stronger demand for goods and services. In the AD–AS model, this is shown by a **rightward shift of the aggregate demand curve**.

> **Key Term: demand-pull inflation**
> Inflation caused by an increase in aggregate demand; in the AD–AS model, AD shifts right.

If you draw the graph, the vertical axis is **price level** and the horizontal axis is **real GDP**. Start with AD and SRAS crossing at an initial equilibrium. Then shift AD to the right. The new equilibrium has:

- a **higher price level**
- a **higher real GDP** in the short run

That pattern matters. If both price level and output rise together, think **demand-pull inflation**.

Why does this happen? Because firms respond to stronger spending by producing more. In the short run, prices of outputs can rise faster than some input costs, so firms expand production. That is why short-run output increases.

Common causes of an AD increase include:

- higher **consumer spending**
- higher **business investment**
- higher **government spending**
- higher **net exports**
- expansionary monetary policy that lowers interest rates
- tax cuts that raise disposable income

A simple way to think about it is “more spending chasing current output.”

Suppose households become more confident and buy more cars, furniture, and vacations. Firms notice sales rising. They increase production and hire more workers. The economy moves to a higher short-run equilibrium. Price level rises because stronger demand puts pressure on available output. Real GDP rises because firms respond by producing more.

This is why demand-pull inflation is often linked to a booming economy or an economy already close to full employment. When there is little unused capacity left, an AD increase creates even more inflation pressure because firms cannot raise output by much before running into labor and input shortages.

> **Key Term: aggregate demand (AD)**
> The total demand for domestically produced final goods and services in an economy.

A useful AP connection is the spending formula:

$$
AD = C + I + G + (X - M)
$$

If one or more of these components increases, AD can shift right. For example:

- **C rises** if households spend more
- **I rises** if firms become more confident
- **G rises** if the government expands spending
- **X - M rises** if exports grow faster than imports

Students often memorize that AD right means inflation, but that is incomplete. On the exam, you must also say that **real GDP rises in the short run**.

> **Test Tip:** If a question says the price level rises and real GDP also rises, the safest answer is usually **demand-pull inflation** caused by **AD shifting right**.

### Cost-push inflation: inflation caused by rising production costs

**Cost-push inflation** happens when firms face higher production costs and reduce the amount they are willing to produce at each price level. In the AD–AS model, this is shown by a **leftward shift of SRAS**.

> **Key Term: cost-push inflation**
> Inflation caused by a decrease in short-run aggregate supply, usually because production costs rise.

This time, start from an initial equilibrium and shift **SRAS left** while AD stays the same. The new short-run equilibrium has:

- a **higher price level**
- a **lower real GDP**

That is the crucial difference from demand-pull inflation. Both types raise the price level, but only cost-push inflation clearly reduces output in the short run.

Why does output fall? Because firms cannot profitably produce as much as before. If wages, oil, imported inputs, or raw materials become more expensive, firms cut production. Less output reaches the market even though the price level is higher.

Common causes of an SRAS decrease include:

- higher **nominal wages**
- higher **oil or energy prices**
- higher **raw material prices**
- supply-chain disruptions
- higher **expected inflation**
- destruction of productive capacity
- other **negative supply shocks**
  > **Key Term: negative supply shock**
  > An event that raises production costs or reduces short-run aggregate supply, shifting SRAS left.

Consider a sharp rise in oil prices. Oil is used in transport, manufacturing, heating, and packaging. That means many firms face higher costs at the same time. They cut production. The economy ends up with a higher price level but lower real GDP.

This explains why cost-push inflation is often more painful for policymakers. With demand-pull inflation, reducing aggregate demand can lower inflation, though it may slow growth. With cost-push inflation, the economy already has inflation **and** weak output. Fighting inflation may worsen unemployment, while boosting output may worsen inflation.

That problem leads directly to **stagflation**.

> **Key Term: stagflation**
> A situation where the price level rises while real GDP falls and unemployment increases, usually because SRAS shifts left.

Stagflation is one of the most tested applications of cost-push inflation. If the prompt says “inflation plus recession” or “higher prices and higher unemployment,” think **SRAS left**.

A classic historical example is the **1970s oil shocks**. Oil prices rose sharply after supply restrictions. Because oil was a major input, firms across the economy faced higher costs. SRAS shifted left. The result was rising price level, falling output, and higher unemployment.

> **Test Tip:** If inflation comes with **falling output** or **higher unemployment**, do not choose demand-pull inflation. That pattern points to **cost-push inflation** and an **SRAS left shift**.

### How to tell them apart on graphs and in questions

This topic becomes much easier if you compare the two patterns directly.

| Type of inflation     | Curve shift | Price level | Real GDP | Typical cause           |
| --------------------- | ----------- | ----------: | -------: | ----------------------- |
| Demand-pull inflation | AD right    |          Up |       Up | More spending           |
| Cost-push inflation   | SRAS left   |          Up |     Down | Higher production costs |

That table gives the exam shortcut, but you still need the reasoning.

If a prompt says:

- consumers spend more
- the government increases spending
- investment rises
- the Fed lowers interest rates

then the likely story is **AD right** and **demand-pull inflation**.

If a prompt says:

- wages rise
- oil prices rise
- imported components become more expensive
- supply chains are disrupted
- a hurricane destroys factories

then the likely story is **SRAS left** and **cost-push inflation**.

Students also confuse a **movement along SRAS** with a **shift of SRAS**. This matters. A change in the **price level** alone causes movement along a given SRAS curve. But cost-push inflation is not movement along SRAS. It is a **leftward shift of the whole SRAS curve** because firms’ costs changed.

Likewise, demand-pull inflation is not movement along AD from a price-level change. It is a **rightward shift of the whole AD curve** because one of the spending components changed.

> **Key Term: short-run aggregate supply (SRAS)**
> The quantity of real GDP firms are willing to produce at different price levels in the short run.

Another important AP distinction is the role of **full employment output**. If the economy is already near LRAS, a further increase in AD is especially inflationary. Firms have less room to raise output before labor markets tighten and input prices rise. So near full employment, demand-pull inflation becomes more severe.

By contrast, if SRAS shifts left from an initial full-employment equilibrium, the new equilibrium ends up left of LRAS. That means the economy now has both inflation and a recessionary gap. This is another way to explain stagflation.

> **Key Term: full employment output**
> The level of real GDP produced when the economy is using resources at its normal sustainable level; shown by LRAS.

### Applying this in AP FRQs and multiple-choice questions

On AP Macroeconomics questions, your answer should follow a clear chain of reasoning:

1. Identify the shock
2. State which curve shifts
3. State the direction of the shift
4. Give the short-run effect on price level
5. Give the short-run effect on real GDP
6. If relevant, mention unemployment

Here is a worked example.

A prompt says: “Energy prices rise sharply across the economy.”

Reasoning:

- Energy is an input cost
- Higher input costs reduce SRAS
- **SRAS shifts left**
- **Price level increases**
- **Real GDP decreases**
- unemployment tends to increase

A different prompt says: “Government spending rises during an expansion.”

Reasoning:

- Government spending is part of AD
- **AD shifts right**
- **Price level increases**
- **Real GDP increases in the short run**
- unemployment tends to fall

For FRQs, write in this style:
“An increase in oil prices raises firms’ per-unit production costs, shifting SRAS left. In the short run, the equilibrium price level rises while real GDP falls.”

That is much stronger than saying only “inflation occurs.”

A common student weakness is giving the same answer for every inflation question. AP examiners want the cause and the output effect. Saying “prices rise” is rarely enough.

Common errors to avoid:

- saying cost-push inflation is caused by AD rising
- saying demand-pull inflation lowers output
- forgetting to mention **short run**
- mixing up **price level** with the inflation rate
- failing to label **AD**, **SRAS**, **LRAS**, **price level**, and **real GDP** on graphs
  > **Test Tip:** In FRQs, use the sequence **shock → curve shift → new equilibrium → price level/output change**. That structure helps you earn points step by step.

## Key Point Checklist

_This article has covered the following key knowledge points:_

- Inflation in the AD–AS model can come from either the demand side or the supply side
- **Demand-pull inflation** is caused by an **increase in aggregate demand**
- On an AD–AS graph, demand-pull inflation is shown by an **AD right shift**
- Demand-pull inflation raises the **price level** and **real GDP** in the short run
- Higher consumer spending, investment, government spending, or net exports can raise AD
- **Cost-push inflation** is caused by a **decrease in short-run aggregate supply**
- On an AD–AS graph, cost-push inflation is shown by an **SRAS left shift**
- Cost-push inflation raises the **price level** but lowers **real GDP** in the short run
- Higher wages, energy prices, and raw material costs can shift SRAS left
- **Stagflation** means rising price level with falling output and higher unemployment
- Stagflation is usually linked to **cost-push inflation**, not demand-pull inflation
- A key exam rule is: **prices up + output up = demand-pull; prices up + output down = cost-push**

## Key Terms and Concepts

- inflation
- demand-pull inflation
- aggregate demand (AD)
- cost-push inflation
- negative supply shock
- stagflation
- short-run aggregate supply (SRAS)
- full employment output


Changes in the AD–AS Model in the Short Run - Inflation can be demand or cost