In: Economics
Given the following information
G = 300
T = 200
C = 220 + .6 (Y-T)
I = 100 – 4r
Md = .75Y – 6r
Ms = 735
a. Derive the IS and LM curves. Calculate the equilibrium values of Y and r.
b. Suppose that G is reduced until the budget deficit is eliminated. Calculate the new equilibrium values of Y and r. Explain the intuition of what happened, providing an IS/LM graph to illustrate.
(a)
In goods market equilibrium, Y = C + I + G
Y = 220 + 0.6(Y - 200) + 100 - 4r + 300
Y = 620 + 0.6Y - 120 - 4r
0.4Y = 500 - 4r
Y = 1250 - 10r (Equation of IS curve)
In money market equilibrium, Md = Ms.
0.75Y - 6r = 735
0.75Y = 735 + 6r
Y = 980 + 8r (Equation of LM curve)
In equilibrium, YIS = YLM.
1250 - 10r = 980 + 8r
18r = 270
r = 15
Y = 1250 - (10 x 15) = 1250 - 150 = 1100
(b)
If budget deficit is zero, it means T = G = 200.
From IS equation,
Y = 220 + 0.6(Y - 200) + 100 - 4r + 200
Y = 520 + 0.6Y - 120 - 4r
0.4Y = 400 - 4r
Y = 1000 - 10r (Equation of new IS curve)
Equating with LM equation,
1000 - 10r = 980 + 8r
18r = 20
r = 1.11
Y = 1000 - (10 x 1.11) = 1000 - 11.1 = 988.9
It is seen that both Y and r have decreased. This is because a decrease in G will shift the IS curve leftward, which lowers both real interest rate and output.
In following graph, IS0 and LM0 are initial IS and LM curves intersecting at point A with initial equilibrium interest rate r0 and initial equilibrium output (GDP) Y0. When government spending decreases, IS0 shifts left to IS1, intersecting LM0 at point B with lower interest rate r1 and lower GDP Y1.