Aggregate Expenditures Line

The two basic types of expenditures--autonomous and induced--are indicated by the aggregate expenditures line.

• Autonomous expenditures are the vertical intercept, or Y-intercept, of the aggregate expenditures line. This is the sum of autonomous consumption, autonomous investment, autonomous government purchases, and autonomous net exports, with an adjustment for autonomous taxes.


• Induced expenditures are the slope of the aggregate expenditures line. The marginal propensity to consume (MPC), which is the slope of the consumption line, forms the foundation of the slope of the aggregate expenditures line. This slope, however, is augmented by the marginal propensity to invest (MPI), marginal propensity for government purchases (MPG), and marginal propensity to import (MPM).

The intercept of the aggregate expenditures line indicates the intersection point between the aggregate expenditures line and the vertical expenditures axis. The aggregate expenditures line intersects the vertical axis in this exhibit at a value of $5 trillion. Theoretically, this is a minimum "baseline" level of aggregate expenditures, the amount of investment undertaken if income and production fall to zero. This intersection indicates autonomous expenditures--aggregate expenditures unrelated to income. Click the [Intercept] button to illustrate.

Autonomous expenditures are aggregate expenditures by the household, business, government, and foreign sectors that are unrelated to and unaffected by the level of income or production. This is best indicated by a zero level of income. While individuals, business firms, government agencies, or foreign entities might occasionally come face-to-face with autonomous expenditures, as their own slice of aggregate income drops to zero, for the aggregate economy autonomous expenditures is mostly an unlikely theoretical extrapolation.