CHAPTER

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Aggregate Demand, Aggregate Supply, and Inflation

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Principles of Economics, 7/e

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The Aggregate Demand Curve

___________________________________ • Aggregate demand is the total demand for goods and services in the economy.

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Deriving the Aggregate Demand Curve

___________________________________ • To derive the aggregate demand curve, we examine what happens to aggregate output (income) (Y) when the price level (P) changes, assuming no changes in government spending (G), net taxes (T), or the monetary policy variable (Ms).

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Deriving the Aggregate Demand Curve

___________________________________ The Impact of an Increase in the Price Level on the Economy – Assuming No Changes in G, T, and Ms

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↑ P → M d ↑ → r ↑ → I ↓ → AE ↓ → Y ↓

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Deriving the Aggregate Demand Curve

___________________________________ • The aggregate demand (AD) curve is a curve that shows the negative relationship between aggregate output (income) and the price level.

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The Aggregate Demand Curve: A Warning

___________________________________ • The AD curve is not a market demand curve. It is a more complex concept.

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• We cannot use the ceteris paribus assumption to draw an AD curve. In reality, many prices (including input prices) rise together.

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The Aggregate Demand Curve: A Warning

___________________________________ • A higher price level causes the demand for money to rise, which causes the interest rate to rise.

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• Then, the higher interest rate causes aggregate output to fall.

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The Aggregate Demand Curve: A Warning

___________________________________ • At all points along the AD curve, both the goods market and the money market are in equilibrium.

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Other Reasons for a DownwardSloping Aggregate Demand Curve

___________________________________ • The consumption link: The decrease in consumption brought about by an increase in the interest rate contributes to the overall decrease in output.

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Other Reasons for a DownwardSloping Aggregate Demand Curve

___________________________________ • The real wealth effect, or real balance, effect is the change in consumption brought about by a change in real wealth that results from a change in the price level.

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Aggregate Expenditure and Aggregate Demand

___________________________________ • At every point along the aggregate demand curve, the aggregate quantity of output demanded is exactly equal to planned aggregate expenditure.

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Y=C+I+G equilibrium condition

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Shifts of the Aggregate Demand Curve

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• An increase in the quantity of money supplied at a given price level shifts the aggregate demand curve to the right.

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Shifts of the Aggregate Demand Curve

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• An increase in government purchases or a decrease in net taxes shifts the aggregate demand curve to the right.

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Shifts of the Aggregate Demand Curve

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Factors That Shift the Aggregate Demand Curve Expansionary monetary policy

Contractionary monetary policy

Ms

Ms

AD curve shifts to the right

Expansionary fiscal policy

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AD curve shifts to the left

Contractionary fiscal policy

G

AD curve shifts to the right

G

AD curve shifts to the left

T

AD curve shifts to the right

T

AD curve shifts to the left

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The Aggregate Supply Curve

___________________________________ • Aggregate supply is the total supply of all goods and services in the economy.

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The Aggregate Supply Curve

___________________________________ • The aggregate supply (AS) curve is a graph that shows the relationship between the aggregate quantity of output supplied by all firms in an economy and the overall price level.

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The Aggregate Supply Curve: A Warning

___________________________________ • The aggregate supply curve is not a market supply curve or the sum of all the individual supply curves in the economy.

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The Aggregate Supply Curve: A Warning

___________________________________ • Firms do not simply respond to market-determined prices, but they actually set prices. Price-setting firms do not have individual supply curves because these firms are choosing both output and price at the same time.

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The Aggregate Supply Curve: A Warning

___________________________________ • When we draw a firm’s supply curve, we assume that input prices are constant. In macroeconomics, an increase in the overall price level means that at least some input prices will be rising as well.

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• The outputs of some firms are the inputs of other firms.

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The Aggregate Supply Curve: A Warning

___________________________________ • Rather than an aggregate supply curve, what does exist is a “price/output response” curve — a curve that traces out the price and output decisions of all the markets and firms in the economy under a given set of circumstances.

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Aggregate Supply in the Short Run

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___________________________________ • In the short run, the aggregate supply curve (the price/output response curve) has a positive slope.

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Aggregate Supply in the Short Run

___________________________________ • At low levels of aggregate output, the curve is fairly flat. As the economy approaches capacity, the curve becomes nearly vertical. At capacity, the curve is vertical.

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Aggregate Supply in the Short Run

___________________________________ • Macroeconomists focus on whether or not the economy as a whole is operating at full capacity.

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• As the economy approaches maximum capacity, firms respond to further increases in demand only by raising prices.

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Output Levels and Price/Output Responses

___________________________________ • When the economy is operating at low levels of output, an increase in aggregate demand is likely to result in an increase in output with little or no increase in the overall price level.

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The Response of Input Prices to Changes in the Overall Price Level

___________________________________ • There must be a lag between changes in input prices and changes in output prices, otherwise the aggregate supply (price/output response) curve would be vertical.

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The Response of Input Prices to Changes in the Overall Price Level

___________________________________ • Wage rates may increase at exactly the same rate as the overall price level if the pricelevel increase is fully anticipated. Most input prices, however, tend to lag increases in output prices.

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Shifts of the Short-Run Aggregate Supply Curve

___________________________________ • A cost shock, or supply shock, is a change in costs that shifts the aggregate supply (AS) curve.

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Shifts of the Short-Run Aggregate Supply Curve

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Factors That Shift the Aggregate Supply Curve Shifts to the Right

Shifts to the Left

Increases in Aggregate Supply

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Decreases in Aggregate Supply

Lower costs lower input prices lower wage rates

Higher costs higher input prices higher wage rates

Economic growth more capital more labor technological change

Stagnation capital deterioration

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Public policy supply-side policies tax cuts deregulation

Public policy waste and inefficiency over-regulation

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Good weather

Bad weather, natural disasters, destruction from wars

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The Equilibrium Price Level

___________________________________ • The equilibrium price level is the point at which the aggregate demand and aggregate supply curves intersect.

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The Equilibrium Price Level

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___________________________________ • P0 and Y0 correspond to equilibrium in the goods market and the money market and a set of price/output decisions on the part of all the firms in the economy.

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The Long-Run Aggregate Supply Curve

___________________________________ • Costs lag behind pricelevel changes in the short run, resulting in an upward-sloping AS curve. • Costs and the price level move in tandem in the long run, and the AS curve is vertical.

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The Long-Run Aggregate Supply Curve

___________________________________ • Output can be pushed above potential GDP by higher aggregate demand. The aggregate price level also rises.

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The Long-Run Aggregate Supply Curve

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___________________________________ • When output is pushed above potential, there is upward pressure on costs, and this causes the shortrun AS curve to the left.

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• Costs ultimately increase by the same percentage as the price level, and the quantity supplied ends up back at Y0.

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The Long-Run Aggregate Supply Curve

___________________________________ • Y0 represents the level of output that can be sustained in the long run without inflation. It is also called potential output or potential GDP.

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Aggregate Demand, Aggregate Supply, and Monetary and Fiscal Policy

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• AD can shift to the right for a number of reasons, including an increase in the money supply, a tax cut, or an increase in government spending. • Expansionary policy works well when the economy is on the flat portion of the AS curve, causing little change in P relative to the output increase.

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Aggregate Demand, Aggregate Supply, and Monetary and Fiscal Policy

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• On the steep portion of the AS curve, expansionary policy does not work well. The multiplier is close to zero.

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• When the economy is operating near full capacity, an increase in AD will result in an increase in the price level with little increase in output.

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Long-Run Aggregate Supply and Policy Effects

___________________________________ • If the AS curve is vertical in the long run, neither monetary policy nor fiscal policy has any effect on aggregate output. • In the long run, the multiplier effect of a change in government spending or taxes on aggregate output is zero.

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The Simple “Keynesian” Aggregate Supply Curve

___________________________________ • The output of the economy cannot exceed the maximum output of YF. • The difference between planned aggregate expenditure and aggregate output at full capacity is sometimes referred to as an inflationary gap.

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Causes of Inflation

___________________________________ • Inflation is an increase in the overall price level.

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• Sustained inflation occurs when the overall price level continues to rise over some fairly long period of time.

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Causes of Inflation

___________________________________ • Demand-pull inflation is inflation initiated by an increase in aggregate demand.

• Cost-push, or supplyside, inflation is inflation caused by an increase in costs.

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Cost-Push, or Supply-Side Inflation

___________________________________ • Stagflation occurs when output is falling at the same time that prices are rising. • One possible cause of stagflation is an increase in costs.

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Cost-Push, or Supply-Side Inflation

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___________________________________ • Cost shocks are bad news for policy makers. The only way to counter the output loss is by having the price level increase even more than it would without the policy action.

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Expectations and Inflation

___________________________________ • If every firm expects every other firm to raise prices by 10%, every firm will raise prices by about 10%. This is how expectations can get “built into the system.”

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• In terms of the AD/AS diagram, an increase in inflationary expectations shifts the AS curve to the left.

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Money and Inflation

___________________________________ • Hyperinflation is a period of very rapid increases in the price level.

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Money and Inflation

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___________________________________ • An increase in G with the money supply constant shifts the AD curve from AD0 to AD1. This leads to an increase in the interest rate and crowding out of planned investment.

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Money and Inflation

___________________________________ • If the Fed tries to prevent crowding, it will increase the money supply and the AD curve will shift farther and farther to the right. The result is a sustained inflation, perhaps hyperinflation.

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Review Terms and Concepts

___________________________________ aggregate demand

hyperinflation

aggregate demand (AD (AD)) curve

inflation

aggregate supply

inflationary gap

aggregate supply (AS (AS)) curve

potential output, or potential GDP

costcost-push, or supplysupply-side, inflation

real wealth, or real balance, effect

cost shock, or supply shock

stagflation

demanddemand-pull inflation

sustained inflation

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equilibrium price level

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