Lecture 9
THE CONSUMPTION FUNCTION
1. Assumptions in our models
- Depreciation = Indirect business taxes = 0
GDP = National income
- Corporate profits taxes = payroll taxes = 0
DI = GDP - Personal taxes (T)
2. Exogenous and Endogenous variables
- Does the model "explain" a particular variable?
- Exogenous variables are "given" (assumed to be fixed)
3. The Consumption Function
- C = a + b(DI)
- Relates (real) consumption spending to (real) disposable income
- Positive slope
- Marginal Propensity to Consume (MPC): 0 < b < 1
3.1 Shifts of the consumption function caused by:
- Changes in wealth
- Changes in the price level (P) - real balance effect
- Changes in expected future income
- Changes in taxes
3.2 Permanent vs. temporary tax cuts
4. The Saving Function
- S = DI - C
- Marginal Propensity to Save (MPS)
- Why is MPC + MPS = 1?
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