Explain Given Economic Outcomes
Core Concepts
This domain asks you to explain why outcomes occur using models. You must connect events to shifts in supply, demand, or aggregate supply/demand, and trace the effects on price, output, employment, and inflation. Key concepts: demand-pull inflation, cost-push inflation, multiplier effect, crowding out, Phillips curve, economic growth, and business cycle.
Explanations to Master
- Demand-pull inflation: AD shifts right → price level rises, real GDP temporarily above potential.
- Cost-push inflation: SRAS shifts left → price level rises, real GDP falls (stagflation).
- Multiplier: An initial change in spending leads to a larger change in GDP; multiplier = 1/(1−MPC) or 1/MPS.
- Crowding out: Government borrowing increases interest rates, reducing private investment.
- Phillips curve: Short-run trade-off between inflation and unemployment; long-run vertical at natural rate.
Common Traps
- Assuming a supply shock shifts AD; it shifts SRAS.
- Forgetting that the multiplier applies to autonomous spending changes, not to price-level-induced movements.
- Confusing short-run and long-run Phillips curves.
- Overlooking that crowding out is partial, not complete, in most models.
Worked Example
If MPC = 0.8, the multiplier is 1/(1−0.8) = 5. A $10 billion increase in government spending shifts AD right by up to $50 billion, assuming no crowding out and constant price level. This raises real GDP and lowers unemployment in the short run, but may cause inflation if the economy is near potential.
Rule of thumb: For any event, ask: which curve shifts, which direction, and what happens to equilibrium price and quantity (or price level and real GDP)?