Module 4: Aggregate Models and Fiscal Policy Module 4: Aggregate Models and Fiscal Policy 4.1 The Aggregate Demand-Aggregate Supply (AS/AD) Model The Aggregate Supply and Aggregate Demand (AS/AD) model is the cornerstone of modern macroeconomics.
It provides a framework for analyzing the entire economy’s output (real GDP) and its overall price level.
This model allows us to see how economic shocks, policy changes, and other events affect the key macroeconomic goals of full employment, price stability, and economic growth.
Aggregate Demand (AD) Aggregate Demand (AD) represents the total amount of real output (goods and services) that all buyers in an economy—consumers, businesses, the government, and foreigners—collectively desire to purchase at each possible price level.
The AD curve slopes downward for three primary reasons: The Real-Balance Effect: As the price level falls, the real value (or purchasing power) of money increases.
This makes consumers wealthier, encouraging them to spend more.
Conversely, a higher price level erodes purchasing power and reduces consumption.
The Interest-Rate Effect: A lower price level reduces the demand for money.
With less demand for money, interest rates fall, which encourages businesses to increase investment spending and consumers to make large purchases.
A higher price level increases the demand for money, driving up interest rates and discouraging spending.
The Foreign-Purchases Effect: When the U.S. price level falls relative to foreign price levels, U.S. goods become cheaper for foreigners, increasing exports.
At the same time, foreign goods become more expensive for Americans, decreasing imports.
This rise in net exports increases the quantity of U.S. goods demanded.
Determinants of Aggregate Demand Factors other than the price level can shift the entire AD curve.
These determinants are often organized by the components of GDP: Consumer Spending (C): Wealth: An increase in stock market values or property values makes consumers feel wealthier and spend more, shifting AD right.
Consumer Expectations: Optimism about the future (e.g., job security, expected bonuses) increases current spending, shifting AD right.
Household Debt: High levels of debt may force consumers to cut back on spending to make repayments, shifting AD left.
Taxes: A decrease in personal income taxes increases disposable income and consumption, shifting AD right.
Investment Spending (I): Real Interest Rates: Lower interest rates make borrowing cheaper for firms, encouraging investment in new capital and shifting AD right.
Expected Returns: If firms are optimistic about future profits, they will invest more today, shifting AD right.