Chapter 24: The Aggregate Demand/Aggregate Supply Model

The AD/AS model is one of the most fundamental frameworks in macroeconomics. It brings together total spending (aggregate demand) and total production (aggregate supply) to explain how the economy reaches equilibrium—and why it sometimes ends up in recession, inflation, or both. This chapter builds the model from the ground up and shows how it connects to the three core macroeconomic goals: growth, low unemployment, and low inflation.

Table of Contents

Macroeconomic Perspectives on Demand and Supply
Building the AD/AS Model
Shifts in Aggregate Supply
Shifts in Aggregate Demand
Growth, Unemployment, and Inflation in the AD/AS Model
Keynes’ Law and Say’s Law in the AD/AS Model
Key Takeaways
Practice Questions
Glossary

1. Macroeconomic Perspectives on Demand and Supply

Macroeconomists have long debated: Is the economy driven primarily by supply or by demand? Two competing “laws” summarize the debate.

Say’s Law: Supply Creates Its Own Demand

Say’s Law (named after French economist Jean-Baptiste Say, 1767–1832): “Supply creates its own demand.”

Intuition: Every time a good or service is produced and sold, it generates income for someone—a worker, manager, owner, or input supplier. A given value of supply must create an equivalent value of demand somewhere in the economy.

Say’s Law works well as a long-run approximation. Over decades, as the economy’s productive power grows, total demand grows at roughly the same pace. But it struggles to explain recessions—periods where the economy as a whole shrinks, business failures outnumber successes, and firms lay off workers.

Economists who emphasize supply-side forces are called neoclassical economists.

Keynes’ Law: Demand Creates Its Own Supply

Keynes’ Law (named after John Maynard Keynes, 1883–1946): “Demand creates its own supply.”

Intuition: During the Great Depression, factories, workers, and technology hadn’t disappeared—but production collapsed. The economy wasn’t producing at full potential because there wasn’t enough demand. The level of GDP was determined not by what the economy could supply, but by how much total demand existed.

Keynes’ Law works well in the short run (months to a few years). But demand alone can’t determine the size of the economy—there are real limits set by labor, capital, technology, and institutions. The government can’t simply pump up demand without limit.

Combining Both

The Synthesis:

Short run: Keynes’ Law dominates—aggregate demand determines output
Long run: Say’s Law dominates—aggregate supply determines output
A complete macroeconomic model needs both supply and demand

2. Building the AD/AS Model

The Aggregate Supply (AS) Curve

Aggregate Supply (AS): The total quantity of output (real GDP) that firms will produce and sell at each price level. The AS curve shows this relationship graphically.

Axes:

Horizontal axis: Real GDP (adjusted for inflation)
Vertical axis: Price level (an index like the GDP Deflator—not the inflation rate, but the average level of prices)

Why AS slopes upward: The price level on the vertical axis represents prices for final outputs, not input prices. If the price of what firms sell rises while their costs of production stay constant, higher profits induce firms to expand production.

The Shape of the AS Curve:

Zone	Shape	Economic Situation
Far left	Nearly flat	High unemployment, many idle factories—a small price increase triggers a large output surge
Middle	Upward-sloping	Economy approaching capacity—output still responds to price increases but less dramatically
Far right	Nearly vertical	All labor and capital fully employed—higher prices cannot induce additional output

Potential GDP and Full-Employment GDP

Potential GDP (Full-Employment GDP): The maximum quantity an economy can produce by fully employing its existing levels of labor, physical capital, and technology, given its market and legal institutions. Shown as a vertical line on the AD/AS diagram.

Can the economy produce beyond potential GDP? Yes, but only temporarily. If output prices are high enough, firms make fanatical efforts: double overtime, machines running 24/7. This hyper-intense production goes beyond sustainable use of resources—the economy can “sprint” above potential GDP in the short run but cannot sustain it.

Short-Run vs. Long-Run Aggregate Supply

SRAS (Short-Run Aggregate Supply): The upward-sloping curve described above, where input prices are held constant
LRAS (Long-Run Aggregate Supply): A vertical line at potential GDP—in the long run, output is determined by productive capacity, not the price level

The Aggregate Demand (AD) Curve

Aggregate Demand (AD): The total spending on domestic goods and services at each price level. It includes all four components:

\[AD = C + I + G + (X - M)\]

Where $ C $ = consumption, $ I $ = investment, $ G $ = government spending, $ X $ = exports, $ M $ = imports.

Why AD slopes downward (three effects):

Effect	Mechanism
Wealth effect	Higher price level → buying power of savings diminishes → consumption falls
Interest rate effect	Higher prices → more money/credit needed for purchases → interest rates rise → borrowing and investment fall
Foreign price effect	Higher domestic prices → U.S. goods become relatively expensive → exports fall, imports rise → net exports decline

AD ≠ Microeconomic Demand! The AD curve looks similar to a micro demand curve, but the axes, concepts, and reasons for the slopes are entirely different:

Micro: Price of one good vs. quantity of that good; slopes down due to substitutes
Macro: Average price level of all goods vs. total real GDP; slopes down due to wealth, interest rate, and foreign price effects

Equilibrium

The intersection of AD and AS determines the equilibrium price level and equilibrium real GDP. At equilibrium, the total amount firms want to produce equals the total amount buyers want to spend.

Worked Example: The Economy of Xurbia

Price Level	AD	AS
110	$700	$600
120	$690	$640
130	$680	$680
140	$670	$720
150	$660	$740

Equilibrium: Price level = 130, Real GDP = $680.

Since equilibrium ($680) is well below where AS becomes steep (~$750), this economy is far from potential GDP. Diagnosis: High unemployment, but little inflationary pressure—a classic recession scenario.

Solving AD/AS with Linear Equations

Problem: Suppose the economy is described by:

$AD: \quad Y = 2{,}000 - 5P$ $SRAS: \quad Y = -200 + 10P$

where $Y$ = real GDP (billions), $P$ = price level index.

Potential GDP = $1{,}350$ billion.

Step 1: Find equilibrium. Set $AD = SRAS$:

$2{,}000 - 5P = -200 + 10P$ $2{,}200 = 15P$ $P^* = 146.7$ $Y^* = 2{,}000 - 5(146.7) = 1{,}267 \text{ billion}$

Step 2: Diagnose. Since $Y^* = 1{,}267 < 1{,}350 = Y_p$, the economy has a recessionary gap of $1{,}350 - 1{,}267 = $83$ billion.

Step 3: Policy. If the government increases spending, shifting AD right by $$150B$:

$AD': \quad Y = 2{,}150 - 5P$ $2{,}150 - 5P = -200 + 10P \implies P^{**} = 156.7, \quad Y^{**} = 1{,}367$

The economy now slightly overshoots potential GDP ($1{,}367 > 1{,}350$), with the price level rising from 146.7 to 156.7 — a 6.8% increase. The output gain of $100B came with some inflation because the economy crossed into the intermediate/neoclassical zone.

3. Shifts in Aggregate Supply

Productivity Growth Shifts AS Right

In the long run, the most important factor shifting the AS curve is productivity growth—how much output can be produced per worker. Historically, U.S. real GDP per capita has grown about 2–3% per year.

Higher productivity → SRAS shifts right (firms can produce more at every price level)
Potential GDP (LRAS) also shifts right → full employment corresponds to a higher output level
Result: Greater real GDP + downward pressure on the price level

Input Price Changes Shift AS

Higher input prices (energy, labor, imported goods) → SRAS shifts LEFT:

At every price level, higher costs discourage production (lower profit margins)
Result: Reduced GDP + higher unemployment + higher price level = stagflation

Lower input prices → SRAS shifts RIGHT:

Result: Economic expansion + lower unemployment + lower inflation

Historical Examples:

Key Distinction: Productivity changes shift both SRAS and LRAS (the economy’s capacity changes). Input price changes shift only SRAS (temporary cost shock, not a permanent capacity change).

Other Supply Shocks

Natural disasters: An early freeze destroying agricultural crops → AS shifts left
Wars: Workers leaving for military service → both SRAS and LRAS shift left
Pandemics: COVID-19 caused worker shortages → SRAS shifted left (chip shortages, meat shortages, service disruptions)

4. Shifts in Aggregate Demand

Since $ AD = C + I + G + (X - M) $, anything that changes these components shifts the AD curve.

Consumer and Business Confidence

Confidence	Effect on AD	Mechanism
Rising confidence	AD shifts right	Consumers spend more, firms invest more
Falling confidence	AD shifts left	Consumers cut back, firms postpone investment

Measuring Confidence:

Consumer confidence: University of Michigan Index—averaged ~90 pre-Great Recession, fell below 60 in late 2008 (lowest since 1980), recovered to upper 90s in 2010s, dropped to lower 70s during COVID-19
Business confidence: OECD Business Tendency Surveys—tracks selling price expectations, employment outlook across 21 countries

Confidence can change for non-economic reasons too: war risks, election results, foreign policy events. U.S. presidents must be careful—pessimistic pronouncements can become self-fulfilling prophecies, reducing confidence and shifting AD left.

Government Macroeconomic Policy

Government spending (G):

Higher G → AD shifts right
Lower G → AD shifts left
Example: U.S. government spending ranged from 17.8% of GDP (1998) to 21.4% (2009, peak of Great Recession)

Tax policy:

Tax cuts → consumers have more disposable income → C rises → AD shifts right
Tax increases → AD shifts left
Tax incentives for businesses → I rises → AD shifts right

Do Economists Favor Tax Cuts? It depends on context:

During recession (equilibrium far below potential GDP): Tax cuts make sense—they shift AD right, boosting output and employment with little inflation risk
During economic boom (near potential GDP): Tax cuts may cause inflationary pressure with little GDP gain
The 1981 Reagan tax cuts and 2001 Bush tax cuts came during recessions—most economists view those as defensible. Tax cuts during booms are more controversial.

Monetary policy (Federal Reserve):

Lower interest rates → encourages borrowing → C and I rise → AD shifts right
Higher interest rates → discourages borrowing → AD shifts left

About Imports in the AD Formula

Why subtract imports? The formula $ AD = C + I + G + X - M $ subtracts imports because AD measures spending on domestically produced goods and services. When an American buys a foreign product, it’s counted in consumption (C) but the income goes to foreign producers. The $-M$ term cancels out the foreign products already included in C, I, and G.

Imports are not bad for the economy—every negative in the M term has a corresponding positive in C, I, or G, and they always cancel out.

5. Growth, Unemployment, and Inflation in the AD/AS Model

Economic Growth and Recession

Long-run growth: Represented by a gradual rightward shift of SRAS and LRAS (potential GDP) over time, driven by productivity increases
Recession: Equilibrium is substantially below potential GDP (far to the left of the LRAS line)
Expansion: Equilibrium is close to potential GDP

Unemployment

Cyclical unemployment: Shown by how far the equilibrium is from potential GDP
- Equilibrium near potential GDP → low cyclical unemployment
- Equilibrium far below potential GDP → high cyclical unemployment
Natural rate of unemployment (structural + frictional): Built into what economists mean by “potential GDP”—typically ~5% in the U.S., ~10% in some European economies

Inflation: Two Sources

Source 1: Demand-Pull Inflation — AD shifts right when the economy is already at or near potential GDP, pushing the equilibrium into the steep portion of the SRAS curve. Firms can’t produce more, so the price level rises.

Source 2: Cost-Push Inflation — SRAS shifts left due to higher input prices (oil, wages). The price level rises while output falls—the nasty combination of stagflation.

Why might inflation persist?

Government keeps stimulating: Continually pushing AD right when already in the steep zone
Inflation expectations: If people expect inflation, they build it into wages, prices, and interest rates—creating a self-reinforcing cycle

6. Keynes’ Law and Say’s Law in the AD/AS Model

The SRAS curve can be divided into three zones, each with different economic implications:

The Three Zones

Zone	Location on SRAS	Shape	What Drives Output?	Key Concern
Keynesian zone	Far left	Nearly flat	Changes in AD determine output	Unemployment (inflation is minimal)
Neoclassical zone	Far right	Nearly vertical	AS (potential GDP) determines output	Inflation (unemployment is low)
Intermediate zone	Middle	Upward-sloping	Both AD and AS matter	Trade-off between unemployment and inflation

Keynesian Zone

Equilibrium is far below potential GDP → deep recession
Shifts in AD strongly affect output and employment
Price level barely changes (plenty of idle capacity absorbs demand increases)
Keynes’ Law applies: Demand creates its own supply

Neoclassical Zone

Equilibrium is at or near potential GDP → near full employment
Shifts in AD mainly affect the price level, not output
The only way to increase real GDP is for AS to shift right (productivity growth, more workers)
Say’s Law applies: Supply creates its own demand

Intermediate Zone

Shifts in AD affect both output and the price level
Trade-off: AD shifts right → higher output + higher prices; AD shifts left → lower output + lower prices
This is where the unemployment-inflation trade-off is most visible

Diagnostic Test Approach: Use the zones like a doctor checking symptoms:

Determine which zone the economy is in
Keynesian zone? Focus on boosting AD (fiscal stimulus, tax cuts, lower interest rates)
Neoclassical zone? Focus on AS (productivity improvements, reducing input costs)
Intermediate zone? Balance trade-offs between inflation and unemployment

The COVID-19 Pandemic: Supply or Demand?

The 2020 pandemic-induced recession involved both supply and demand shocks:

Supply side: Workers left the labor market, supply chains broke, chip and meat shortages
Demand side: People couldn’t or wouldn’t travel, dine out, or shop → spending collapsed
Most economists believe it was a combination of both, making it especially challenging for policymakers

7. Key Takeaways

Say’s Law (supply creates demand) works in the long run; Keynes’ Law (demand creates supply) works in the short run. A complete model needs both.
The SRAS curve slopes upward (higher output prices with fixed input prices → more production). It’s flat on the left (idle capacity) and steep on the right (near full employment).
The LRAS curve is vertical at potential GDP—long-run output depends on labor, capital, and technology, not the price level.
The AD curve slopes downward due to the wealth effect, interest rate effect, and foreign price effect. $ AD = C + I + G + (X - M) $.
Productivity growth shifts both SRAS and LRAS right. Input price increases shift only SRAS left (potentially causing stagflation).
Consumer/business confidence, government spending, tax policy, and monetary policy all shift AD.
Demand-pull inflation occurs when AD shifts right near potential GDP. Cost-push inflation occurs when SRAS shifts left.
The SRAS curve has three zones: Keynesian (flat, AD drives output), Neoclassical (steep, AS determines output), and Intermediate (both matter, unemployment-inflation trade-off).

8. Practice Questions

Q1. What is the difference between Say’s Law and Keynes’ Law? In what time horizon does each apply best?

Answer

Say's Law holds that "supply creates its own demand"—producing goods generates enough income to purchase those goods. It applies best in the long run, over periods of years or decades. Keynes' Law holds that "demand creates its own supply"—the level of total spending determines how much firms produce. It applies best in the short run (months to a few years), when the economy may have idle capacity and recessions can occur due to insufficient demand.

Q2. Explain why the SRAS curve is nearly flat on its far left and nearly vertical on its far right.

Answer

On the far left, unemployment is high and many factories are idle. A small price increase creates strong incentives for firms to ramp up production, since workers and machines are readily available—so output increases substantially with little price change (flat curve). On the far right, the economy is at or near potential GDP with nearly all labor and capital fully employed. Higher prices cannot induce much additional output because there simply aren't more workers or machines available—so the price level rises but output barely changes (vertical curve).

Q3. Name the three effects that explain why the AD curve slopes downward and briefly explain each.

Answer

(1) **Wealth effect:** A higher price level reduces the real purchasing power of savings, causing consumers to spend less. (2) **Interest rate effect:** Higher prices increase the demand for money and credit, pushing interest rates up, which reduces borrowing for investment and big purchases. (3) **Foreign price effect:** Higher domestic prices make U.S. goods relatively more expensive than foreign goods, reducing exports and increasing imports, which lowers net exports.

Q4. What is stagflation? What causes it in the AD/AS model?

Answer

Stagflation is the combination of stagnant economic growth (recession), high unemployment, and rising inflation—all occurring simultaneously. In the AD/AS model, it is caused by a leftward shift of the SRAS curve, typically due to a sharp increase in input prices (like oil). The leftward shift reduces output (causing recession and unemployment) while also pushing the price level higher (causing inflation). The U.S. experienced stagflation in the 1970s when oil prices surged.

Q5. Using the AD/AS model, explain the effect of a significant increase in government spending when the economy is in a deep recession.

Answer

In a deep recession, the equilibrium is in the Keynesian zone (far left of SRAS), where the curve is nearly flat. Increased government spending shifts AD to the right. Because the SRAS is flat in this region, the rightward shift of AD primarily increases real GDP and reduces unemployment, with very little increase in the price level. This is why fiscal stimulus during recessions can boost output without much inflation risk.

Q6. How does the AD/AS model illustrate the difference between short-run and long-run economic growth?

Answer

**Short-run:** Growth and recessions are shown by the position of the AD-AS equilibrium relative to potential GDP. A recession occurs when equilibrium is far below potential GDP; an expansion occurs when equilibrium moves closer to potential GDP. **Long-run:** Growth is shown by a gradual rightward shift of both the SRAS and LRAS curves over time, driven by productivity improvements, more workers, and technological progress. The vertical LRAS line at potential GDP moves steadily to the right.

Q7. The economy of Xurbia has a price level equilibrium of 130 and output of $680, while potential GDP is around $750. If the government enacts a tax cut that raises AD by 50 at every price level, what happens to the equilibrium? Should policymakers be concerned about inflation?

Answer

The AD curve shifts right by 50 at every price level. The new equilibrium will be at a higher output level (between $680 and $750) and a somewhat higher price level (above 130). Since the original equilibrium was well below potential GDP (Keynesian zone), the tax cut primarily increases output and employment. Inflation should not be a major concern because the economy still has idle capacity. However, if the shift pushes equilibrium close to potential GDP, some inflationary pressure may begin to emerge.

Q8. Suppose oil prices spike dramatically. Using the AD/AS model, describe the effects on output, unemployment, the price level, and what zone the economy might shift toward.

Answer

A dramatic oil price spike increases input costs across the economy, shifting SRAS to the left. The new equilibrium has lower real GDP (recession), higher unemployment, and a higher price level (inflation)—the classic stagflation scenario. The economy could shift from the intermediate zone deeper into the Keynesian zone if the supply shock is severe enough, with equilibrium moving further below potential GDP.

Q9. Explain why the AD/AS diagram is NOT the same as a microeconomic supply and demand diagram, even though both have two crossing lines.

Answer

Key differences: (1) The vertical axis in micro shows the price of ONE good (relative to other goods); in macro, it shows the overall price LEVEL (an index like the GDP Deflator). (2) The horizontal axis in micro shows the quantity of one product; in macro, it shows total real GDP. (3) The micro demand curve slopes down because of substitute goods; the AD curve slopes down because of the wealth, interest rate, and foreign price effects. (4) The shapes of micro supply curves vary widely; the SRAS curve always has the same characteristic shape (flat left to steep right).

Q10. In which SRAS zone is each of the following policies most effective at increasing real GDP? (a) Increasing government spending (b) Investing in new technology and worker training

Answer

(a) Increasing government spending shifts AD to the right and is most effective at increasing real GDP in the **Keynesian zone** (far left of SRAS), where the curve is flat and output is far below potential GDP. In this zone, AD shifts translate mainly into higher output with little inflation. In the neoclassical zone, the same policy would mainly raise prices, not output. (b) Investing in technology and training increases productivity, shifting both SRAS and LRAS to the right. This is most effective in the **neoclassical zone**, where the economy is already near capacity and the only way to increase real GDP is to expand the economy's productive potential (shift AS right).

Q11. During the COVID-19 pandemic, the U.S. economy experienced both supply and demand shocks. Use the AD/AS model to explain what happened.

Answer

**Supply shock (SRAS shifts left):** Workers left the labor market due to illness, safety concerns, and lockdowns. Supply chains were disrupted, causing shortages of computer chips, meat, and other goods. This reduced the economy's ability to produce, shifting SRAS left. **Demand shock (AD shifts left):** Consumers cut travel, restaurant dining, and shopping. Firms postponed investment due to uncertainty. This reduced total spending, shifting AD left. The combined effect was a sharp drop in real GDP and a rise in unemployment. The supply shock also created upward pressure on prices for scarce goods, while the demand shock created downward pressure. The net effect on prices depended on which shock dominated in each sector—but overall, the economy entered a deep recession followed by inflation as supply constraints persisted while demand recovered.

Q12. If households decide to save more of their income, what happens in the short run via the AD/AS model? What about the long run?

Answer

**Short run:** Higher household saving means lower consumption spending (C falls). This shifts AD to the left, leading to lower real GDP, higher unemployment, and a lower price level—a recessionary effect. **Long run:** Higher saving provides more financial capital for investment. Over time, this additional investment increases the economy's productive capacity, shifting SRAS and LRAS to the right. In the long run, the economy can produce more at every price level, potentially leading to higher output and a lower price level. This is the "paradox of thrift"—what's individually prudent (saving) can be collectively harmful in the short run but beneficial in the long run.

Q13. The economy is described by:

$AD: Y = 3{,}000 - 8P$
$SRAS: Y = -500 + 12P$
Potential GDP = $$1{,}600B$

(a) Find equilibrium price level and real GDP.
(b) Is there a recessionary or inflationary gap? How large?
(c) An oil shock shifts SRAS to $Y = -800 + 12P$. Find the new equilibrium.
(d) Calculate the resulting change in inflation (% change in price level) and the % change in real GDP. What is this scenario called?

Answer

**(a)** Set $AD = SRAS$: $$3{,}000 - 8P = -500 + 12P \implies 3{,}500 = 20P \implies P^* = 175$$ $$Y^* = 3{,}000 - 8(175) = 3{,}000 - 1{,}400 = 1{,}600$$ Equilibrium: $P = 175$, $Y = \$1{,}600B$. The economy is exactly at potential GDP. **(b)** Gap = $1{,}600 - 1{,}600 = 0$. No gap — the economy is at full employment. **(c)** New SRAS: $Y = -800 + 12P$ $$3{,}000 - 8P = -800 + 12P \implies 3{,}800 = 20P \implies P^{**} = 190$$ $$Y^{**} = 3{,}000 - 8(190) = 3{,}000 - 1{,}520 = 1{,}480$$ **(d)** Price level change: $\frac{190 - 175}{175} \times 100 = 8.6\%$ increase (inflation). GDP change: $\frac{1{,}480 - 1{,}600}{1{,}600} \times 100 = -7.5\%$ (recession). This is **stagflation** — simultaneous recession (GDP fell 7.5%) and inflation (prices rose 8.6%), caused by the leftward shift of SRAS from the oil shock.

Q14. The economy of Westland is in the Keynesian zone with equilibrium GDP of $800B and potential GDP of $1{,}200B. The government enacts a $150B fiscal stimulus (increasing G by $150B).

(a) If the SRAS curve is perfectly flat in the Keynesian zone, what happens to GDP and the price level?
(b) If instead the economy were in the neoclassical zone (SRAS nearly vertical), what would the same $150B stimulus do?
(c) Why does the effectiveness of fiscal policy depend on which zone the economy is in?

Answer

**(a)** In the Keynesian zone (flat SRAS), the AD shift right translates **entirely into output:** - GDP increases by $150B (from $800B to $950B) - Price level remains approximately unchanged - The $400B recessionary gap shrinks to $250B - Unemployment falls significantly **(b)** In the neoclassical zone (nearly vertical SRAS), the same AD shift translates **entirely into prices:** - GDP barely changes (already at capacity) - Price level rises substantially - The $150B stimulus creates pure demand-pull inflation - No meaningful reduction in unemployment (already near natural rate) **(c)** Fiscal policy effectiveness depends on **available capacity:** - Keynesian zone: idle workers and factories can absorb new demand → output rises - Neoclassical zone: no spare capacity → new spending just bids up prices - This is why timing fiscal policy is crucial — stimulus during booms causes inflation, while stimulus during deep recessions mainly boosts output

Q15. In 2022, the U.S. experienced approximately 9.1% CPI inflation (peak in June) alongside 3.5% unemployment (near historic lows). Using the AD/AS model:

(a) Which zone of the SRAS curve was the U.S. economy likely operating in? How do you know?
(b) Was the inflation primarily demand-pull, cost-push, or both? Provide evidence for each.
(c) The Federal Reserve raised interest rates from near 0% to over 5% in 2022–23. Using the AD/AS framework, explain the mechanism and the expected trade-offs.
(d) By mid-2023, inflation had fallen to about 3% while unemployment remained at 3.6%. Does this outcome surprise you? Why or why not?

Answer

**(a)** The U.S. was in the **neoclassical zone** (or the border with the intermediate zone). Evidence: unemployment at 3.5% was **below** the estimated natural rate (~4–4.5%), meaning the economy was at or slightly above potential GDP. In this zone, further AD increases mainly push prices up rather than boosting output. **(b)** **Both:** - **Demand-pull:** Massive fiscal stimulus ($5+ trillion in COVID relief), pent-up consumer demand, excess savings → AD shifted far right - **Cost-push:** Supply chain disruptions (semiconductor shortages, shipping delays), energy price spikes (Russia-Ukraine war pushed oil above $120/barrel), labor shortages → SRAS shifted left The combination of rightward AD and leftward SRAS meant maximum upward pressure on prices. **(c)** Mechanism: Higher interest rates → borrowing becomes more expensive → consumer spending on big-ticket items (cars, houses) falls, business investment declines → **AD shifts left** → equilibrium moves along SRAS toward lower prices *and* lower output. **Trade-off:** The Fed was deliberately cooling demand to fight inflation, knowing this risked: - Higher unemployment (AD shift left reduces output) - Possible recession (if AD shifts too far left) - Financial market stress (higher rates reduce asset values) **(d)** This outcome is the elusive **"soft landing"** — inflation fell substantially without a recession. It's somewhat surprising because history suggests significant disinflation usually requires a recession (e.g., Volcker's 1980–82 tightening caused 10.8% unemployment). The 2023 soft landing was possible because: - Supply chains healed (SRAS shifted back right), reducing cost-push pressure - Labor force participation recovered - The combination of supply recovery + moderate demand cooling achieved disinflation without crushing output - This was partly a reversal of the temporary SRAS shift, not just a demand-side adjustment

9. Glossary

Term	Definition
Aggregate demand (AD)	Total spending on domestic goods and services in an economy: $ C + I + G + (X - M) $
Aggregate supply (AS)	Total quantity of output (real GDP) that firms will produce and sell at each price level
AD/AS model	Framework showing how aggregate demand and aggregate supply interact to determine equilibrium output and price level
SRAS	Short-run aggregate supply; upward-sloping curve where input prices are held constant
LRAS	Long-run aggregate supply; vertical line at potential GDP showing no relationship between price level and output in the long run
Potential GDP	Maximum output an economy can produce with full employment of labor, capital, and technology
Full-employment GDP	Another name for potential GDP
Say’s Law	“Supply creates its own demand”—emphasizes aggregate supply as the driver of the economy (long-run perspective)
Keynes’ Law	“Demand creates its own supply”—emphasizes aggregate demand as the driver (short-run perspective)
Neoclassical economists	Economists who emphasize the importance of aggregate supply in determining the macroeconomy over the long run
Keynesian zone	Far-left portion of SRAS where the curve is flat; AD determines output with minimal price changes
Neoclassical zone	Far-right portion of SRAS where the curve is steep; AS determines output and AD changes mainly affect prices
Intermediate zone	Middle portion of SRAS; both output and prices change when AD shifts
Stagflation	Stagnant growth combined with high inflation, caused by a leftward shift of SRAS
Wealth effect	Higher price level reduces real value of savings, lowering consumption
Interest rate effect	Higher prices increase demand for money, raising interest rates and reducing investment
Foreign price effect	Higher domestic prices make exports expensive and imports cheap, reducing net exports

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Chapter 24: The Aggregate Demand/Aggregate Supply Model

1. Macroeconomic Perspectives on Demand and Supply

Say’s Law: Supply Creates Its Own Demand

Keynes’ Law: Demand Creates Its Own Supply

Combining Both

2. Building the AD/AS Model

The Aggregate Supply (AS) Curve

Potential GDP and Full-Employment GDP

Short-Run vs. Long-Run Aggregate Supply

The Aggregate Demand (AD) Curve

Equilibrium

Solving AD/AS with Linear Equations

3. Shifts in Aggregate Supply

Productivity Growth Shifts AS Right

Input Price Changes Shift AS

Other Supply Shocks

4. Shifts in Aggregate Demand

Consumer and Business Confidence

Government Macroeconomic Policy

About Imports in the AD Formula

5. Growth, Unemployment, and Inflation in the AD/AS Model

Economic Growth and Recession

Unemployment

Inflation: Two Sources

6. Keynes’ Law and Say’s Law in the AD/AS Model

The Three Zones

Keynesian Zone

Neoclassical Zone

Intermediate Zone

The COVID-19 Pandemic: Supply or Demand?

7. Key Takeaways

8. Practice Questions

9. Glossary