Macroeconomics B Problem set 1 Summer 2022
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Macroeconomics IV/Advanced
Macroeconomics B
Problem set 1
Summer 2022
Question 1
Consider the following utility maximization problem:
{ct ,kt+1>0}0 s.t.
E0 , pt (ln ct + y ln kt+1)┐
kt+1 + ct = A t(1) -a kt(a)
where a e (0, 1), p e (0, 1), y | 0, ct denotes consumption in period t , kt+1 is the amount of capital stock held at the end of period t (and thus at the beginning of period t + 1), and At is the productivity of capital stock in period t .
Assume that
ln At+1 = p ln At + et+1
for all t, where p e (0, 1) and et+1 is an independent white noise.
You can guess and verify that the value function in the Bellman equation for this problem takes the following form:
V (At , kt) = F + G ln At + H ln kt
where F , G , and H are constants.
Suppose that a = 0.6, p = 0.9, y = 0.2, and p = 0.5. Given these parameter values, derive the values of F , G , and H with 2 decimal places (i.e., if the value of F is 1.6875, only answer 1.68). (Note: you do not need to de-trend the model, because there is no trend in At .)
Question 2
Consider the following utility maximization problem for a household:
{ct ,at+1 ,bt1a,dt(x)+1>0}0 pt / + y \
s.t. at+1 + bt+1 + dt+1 + ct = (1 + i)at + (1 + ib)bt + (1 + id)dt
where f | 0, p e (0, 1), y | 0, ct denotes consumption in period t, and at+1 , bt+1 , dt+1 is the amounts of capital stock, government bonds, and bank deposits held at the end of period t (and thus at the beginning of period t + 1). i , ib, and id denote the constant gross rates of return on at , bt, and dt , respectively, at period t . Thus, the household faces no uncertainty.
In the utility maximization problem, qt+1 measures the “liquidity aggregate” that consists of government bonds and bank deposits. The value of this variable represents the amount of convenience provided by the two types of financial assets, which are easily convertible into cash when the household needs to make payments. The utility of this convenience is assumed to be determined by the following function form:
qt 三 [(1 - 入)bt(p) + 入dt(p)]
where 入 e (0, 1) and p ) 1.
In the following questions, you can assume ct | 0, at+1 | 0, bt+1 | 0, and dt+1 | 0 for all t at the optimum.
a. Derive the first order condition for at+1 . Suppose f = 2, p = 0.9, y = 0.2, and i = 0.05. Also, assume ct+1 = 5. What is the value of ct implied by the first order condition for at in this case? Derive the answer with 2 decimal places.
b. In addition, derive the first order conditions for bt+1 and dt+1 . Suppose 入 = 0.5, p = 0.5, i = 0.05, ib = 0.02, id = 0. What is the ratio of bt+1 to dt+1 implied by the
first order conditions in this case? Derive the answer with 2 decimal places.
2022-07-01