How the Macroeconomy Works: Supply and Demand
The economy works through the interaction of aggregate demand (total spending) and aggregate supply (total production). Understanding these forces helps explain everything from inflation to economic growth.
Aggregate Demand (AD) equals consumption + investment + government spending + exports−imports. The AD curve slopes downward because higher prices reduce real income, make imports relatively cheaper, and typically lead to higher interest rates that discourage spending.
Short-run Aggregate Supply (SRAS) slopes upward - higher prices mean more profit, so firms produce more. SRAS shifts when costs change: wage increases, raw material prices, or government regulations can all move the curve.
Long-run Aggregate Supply (LRAS) is vertical because it represents the economy's productive potential. This shifts right with technological advances, better education, demographic changes, or improved competition policy.
The circular flow of income shows how money moves between households and firms. Injections (investment, government spending, exports) expand the economy when they exceed leakages (savings, taxes, imports). When leakages exceed injections, the economy contracts.
Key Point: Economic equilibrium occurs when aggregate demand equals aggregate supply, or when the rate of injections equals the rate of leakages.