Chapter 12: Aggregate Demand and Aggregate Supply

Definition: The aggregate demand curve represents the relationship between the aggregate price level and the total quantity of goods and services demanded by households, firms, the government, and foreign buyers.
Characteristics: The aggregate demand (AD) curve slopes downward, meaning as the price level decreases, the quantity of output demanded increases.
- For example, had the price level in 1933 been 2.5 instead of 5.2, the quantity of output demanded would have increased to $99.3 billion.

Recall: GDP = C + I + G + X - IM

Wealth Effect: A higher aggregate price level reduces the purchasing power of households’ wealth, resulting in decreased consumer spending.
Interest Rate Effect: A higher aggregate price level makes households hold more cash, causing interest rates to rise; this leads to a decrease in both investment spending and consumer spending.

The AD curve is integrated with the income-expenditure model by dropping the assumption of a fixed price level.
Changes in the aggregate price level affect the planned expenditure (AE Planned) curve.
- A drop in the price level results in higher planned expenditures across all output levels, prompting a multiplier process that raises real GDP.

Factors that cause shifts include:
- Expectations: Optimism in consumers and firms leads to increased aggregate expenditure; pessimism decreases expenditure.
- Wealth: Increase in the real value of household assets boosts purchasing power and aggregate expenditure.
- Size of Existing Physical Capital Stock: Firms with ample capital do not feel a need to invest further.
- Fiscal Policy: Changes in government purchases (G), taxes, or transfers impact aggregate demand directly or indirectly.
- Monetary Policy: An increase in money supply lowers interest rates, boosting investment and consumer spending.
Directional Shifts:
- Rightward shifts indicate an increase in quantity output demanded at any price level.
- Leftward shifts indicate a decrease in quantity output demanded.

Movement along the curve occurs when the change in wealth is due to price level fluctuations (e.g., inflation).
Shifts in the curve occur when factors unrelated to price levels change (e.g., a housing market crash).

Definition: The aggregate supply curve illustrates the relationship between the aggregate price level and the quantity of aggregate output that producers are willing to supply.
- There are two types of aggregate supply curves:
1. Short-Run Aggregate Supply (SRAS)
2. Long-Run Aggregate Supply (LRAS)

Positive Relationship: In the short run, an increase in the price level is associated with an increase in the quantity of aggregate output supplied.
- Example: When the price level falls from 6.3 to 5.2, the output supplied decreases from $99.3 billion to $69.4 billion.
Upward Sloping: SRAS curves slope upwards due to factors such as sticky nominal wages (slow to adjust) and pricing strategies in competitive markets.
Profit per Unit Definition:
$\text{Profit per unit} = \text{Price per unit} - \text{Production cost per unit}$
Sticky Wages: Nominal wages do not adjust immediately to changes in economic conditions, thereby impacting aggregate output positively during a rise in prices, since profit margins increase.

Factors that can cause shifts include:
- Commodity Prices: An increase leads to higher production costs, shifting SRAS leftward.
- Nominal Wages: An increase raises production costs, also shifting SRAS leftward.
- Productivity Levels: Improvement in productivity can shift SRAS rightward, indicating higher output at existing prices.

In the long run, nominal wages will fully adjust to the aggregate price level (they are flexible, not sticky). The aggregate price level has no effect on the quantity of aggregate output supplied.
The supply curve shows the relationship between the aggregate price level and the quantity of aggregate output supplied that holds if all prices. (including nominal wages).
The long run is the time it takes for all prices to adjust
Prices have no effect on aggregate output because prices are fully flexible.
Potential output: The level of real GDP the economy would produce if all prices, (including nominal wages) were fully flexible.

Discusses various factors affecting shifts, including those in commodity markets, wage rates, and productivity levels, alongside their effects on aggregate supply, described in Table 12-2.

The economy is in short-run macroeconomic equilibrium when aggregate output supplied equals that demanded.
- Short-Run Equilibrium Aggregate Price Level: The price level at the intersection of the AD and SRAS curves.
- Short-Run Equilibrium Aggregate Output: Quantity produced in short-run equilibrium.

Demand Shock: An event that shifts aggregate demand affects both the aggregate price level and output. A negative demand shock decreases both, while a positive shock increases both.

Long-Run Macroeconomic Equilibrium: Achieved when the economy operates at potential output, represented by the LRAS curve.
Recessionary Gap/Inflationary Gap: Defined with respect to potential output; recessionary occurs when output is below potential and vice versa.
Output Gap Formula:
$\text{Output gap} = \frac{\text{Actual output} - \text{Potential output}}{\text{Potential output}}$

Discussions about the pace of self-correction in economies and the advocacy for active stabilization policies using monetary and fiscal measures to avoid prolonged instability.

Importance of timely policy intervention to mitigate adverse impacts such as high unemployment and deflation.
Consideration of potential long-term costs associated with stabilization interventions.

Responses to negative supply shocks indicate a conflict where policies to lower unemployment could lead to inflation while stabilizing prices would increase unemployment. A historical example from the 1980s Canada illustrates policy choices made during such shocks.

Immediate implications of Macro policy responses to demand shocks, alongside consequences for long-term welfare.
Emphasis on Keynes' critique of focusing solely on the long run and the importance of maintaining stability in the short term while recognizing the necessity for strategic policy responses to economic changes.