Suppose the marginal propensity to consume is 0.75 and the government spending multiplier is 4. If the government decreases its purchases by $100 million, the aggregate demand curve will shift to the by $ million. If the government increases income taxes by $100 million, the aggregate demand curve will shift to the by $ million.

Left by $400; Left by $300

Explanation:

Given that,

Marginal propensity to consume, MPC = 0.75

Government spending multiplier = 4

(a) If the government decreases its purchases by $100 million, then the magnitude of the shift in aggregate demand curve is calculated by multiplying the change in government spending to the government spending multiplier.

Aggregate demand curve shift left by

= Change in government spending × Government spending multiplier

= $100 × 4

= $400 million

(b) If the government increases income taxes by $100 million, then the magnitude of the shift in aggregate demand curve is calculated by multiplying the change in taxes to the tax multiplier.

Tax multiplier:

= MPC ÷ (1 - MPC)

= 0.75 ÷ (1 - 0.75)

= 0.75 ÷ 0.25

= 3

Aggregate demand curve shift left by

= Change in taxes × Tax multiplier

= $100 × 3

= $300 million