22 Lecture Notes for ECON 2030

Definition: The aggregate demand curve (AD) illustrates the relationship between the aggregate price level and the quantity of aggregate output demanded by various sectors which include:
- Households
- Businesses
- Government
- The rest of the world
Graphical Representation: The AD curve is characterized as being downward sloping. This indicates that at a lower aggregate price level, other factors being constant (ceteris paribus), the quantity of aggregate demand increases.
- Key components include:
- Aggregate output (real GDP)
- Inflation rate/price level

Mechanism: When the price level is high, households and firms have less money available for lending. This scarcity leads to an increase in the interest rates. Consequently, higher interest rates discourage spending, leading to a decrease in aggregate expenditure and equilibrium output.
Implication:
- If, for instance, the price level is at $800$ , savings are affected by rising interest rates. This results in reduced spending, as individuals prefer to save more instead of spend.
- The relationship can be summarized in the loanable funds market, where higher savings increase the quantity of funds available for lending, ultimately affecting demand.

Definition: Consumer spending influenced by changes in the aggregate price level that impact the purchasing power of individuals’ assets.
Illustrative Example: Assume a scenario where all prices suddenly drop to half their original level. In this case, individuals feel wealthier due to increased purchasing power, leading to a rise in overall consumption.

The AD curve can shift due to various economic events:
- Right Shift: Indicates an increase in the quantity of aggregate output demanded at any given price level.
- Left Shift: Indicates a decrease in the quantity of aggregate output demanded at any given price level.

Right Shift: Events that encourage consumers to spend more at a given price level, such as:
- Tax cuts
- Stock market booms
Left Shift: Events that decrease consumer spending, for example:
- Tax hikes
- Stock market declines
Example: If Americans suddenly become more concerned about saving for retirement, this change would decrease current consumption, hence shifting the AD curve to the left.
- GDP Identity: $GDP = C + I + G + NX$ where C = Consumption, I = Investment, G = Government Purchases, NX = Net Exports.

Right Shift: Factors like optimism about future economic conditions or a decrease in interest rates can prompt firms to invest more at any given price level.
- An increase in the money supply that lowers interest rates exemplifies this scenario.
Left Shift: Conversely, if firms exhibit pessimism about the future or if interest rates increase due to a money supply contraction, investment will decline.
Example: The introduction of a faster line of computers leads to increased investment by firms in updated technologies.

Right Shift: An increase in government spending on goods and services (e.g., increased spending in defense or infrastructure projects).
Left Shift: A reduction in government expenditures on goods and services (e.g., cuts in defense spending).
Example: A decision by Congress to cut defense procurement can lead to a leftward shift of the AD curve.

Right Shift: Increases in spending on net exports at a given price level, induced by factors such as:
- Economic booms abroad
- Currency depreciation that boosts export attractiveness.
Left Shift: Decreases in net exports due to conditions like recessions abroad or currency appreciation.
Example: A recession in Europe leads to decreased purchases of goods from the United States, adversely affecting US net exports.

The changes in price levels, consumer behavior, investment actions, government policies, and international economic conditions all interplay to influence the shape and position of the aggregate demand curve.