No.PZ2021050707000059 (选择题)
来源:
In a simple economy with no foreign sector, the following equations apply
If the real interest rate is 3% and government spending increases to 2,000, the increase in aggregate income will be closest to:
A 1,000.
B 1,163.
C 7,143.
解析
Solution: C.
With no foreign sector, the GDP identity is Y = C + I + G.
With substitution from the equations above,
Y = 2,500 + 0.80 × (Y – T) + 500 + 0.30 × Y – 25 × r + 1,000
= 2,500 + 0.80 × (Y +250 – 0.30 × Y) + 500 + 0.30 × Y – 25 × r + 1,000.
Y = 4,200 + 0.86 × Y – 25 × r.
Y = 30,000 – 178.6 × r.
At 3%, Y = 30,000 – 178.6 × 3 = 29,464.
Alternatively, Y – 0.86Y = 4,200 – 25 × r
0.14Y = 4,200 – 256 × r.
If government spending increased by 1,000 to 2,000, then Y = 5,200 + 0.86 × Y – 25 × r.
Y = 37,142 – 178.6 × r, which at 3% would be Y = 37,142 – 178.6 × 3 = 36,607.
Representing an increase of 36,607 – 29,464 = 7,143.
Alternatively, at 5,200, Y – 0.86Y = 5,200 – 25 × r or 0.14 Y = 5,200 – 25 × r.
Or more simply, ∆G ÷ (1 – c) = 1,000/(1 – 0.86) = 7,143.
考点：经济- Monetary and Fiscal Policy -Fiscal Policy计算
