In: Economics
Consider the following two-period Fisher model of consumption. Jamil earns $600 in the first period and $0 in the second period. The interest rate is 10 percent. His lifetime utility function is log(?1 ) + 0.5log(?2).
a) Find the optimal values of ?1 and ?2.
Answer: ?? = ???, ?? = ???
b) Suppose that the lifetime utility function changes to log(?1 ) + log(?2). Calculate the new optimal values of ?1 and ?2. How is the optimal value of ?1 in this question compared to the one in the pervious question? What is the intuition behind this change?
Answer: ?? = ???, ?? = ??? .The weight (or time discount factor) multiplied to the second-period utility function is larger, which means that Jamil is more patient. Hence he reduces the first period consumption and increases the second period consumption.
As you may have noticed, I have the answers, I just need to understand the step-by-step process of solving this question.
Income in period 1, Y1 = $600. Income in period 2, Y2 = $0. Interest rate is 10 percent.
Lifetime utility function U = log(?1 ) + 0.5log(?2).
a) Find the optimal values of ?1 and ?2.
Lifetime budget constraint is (1 + 10%)C1 + C2 = (1 + 10%)Y1 + Y2
1.1C1 + C2 = 1.1*600 + 0
1.1C1 + C2 = 660
From the utility function slope = MRS = -MUC1/MUC2 = -(1/C1) / (0.5/C2) = -2C2/C1
Slope of the budget constraint = -1.1/1 = -1.1
At the optimal choice, MRS = slope of the budget constraint
2C2/C1 = 1.1
C2 = 0.55C1
Use this in the budget constraint
1.1C1 + 0.55C1 = 660
C1 = 660/1.65 = 400
C2 = 0.55*400 = 220
Answer: ?? = ???, ?? = ???
b) New lifetime utility function changes to log(?1 ) + log(?2). MRS = -MUC1/MUC2 = -(1/C1) / (1/C2) = -C2/C1
Slope of the budget constraint = -1.1/1 = -1.1
At the optimal choice, MRS = slope of the budget constraint
C2/C1 = 1.1
C2 = 1.1C1
Use this in the budget constraint
1.1C1 + 1.1C1 = 660
C1 = 660/2.2 = 300
C2 = 1.1*300 = 330
Answer: ?? = ???, ?? = ??? .