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Econ 3134

Problem Set 2

1.  Consider the following lottery:

 $40, 000

L = $10, 000

,$5, 000

p = 0.3

p = 0.5

p = 0.2


(a) Assuming u(x) = ,x, calculate

i. E(L)

ii. E(u(L))

iii.  CE(L)

 

(b)  Suppose you can play the lottery twice and average the winnings.

i. What is the resulting distribution over final wealth  (i.e.,  the new lottery)?

ii. Let L2  denote the lottery you get in the previous question. Calculate

CE(L2 ) and compare this to CE(L). Interpret this.

 

2.  Consider a person who is offered a choice between two lotteries:

 

LA : Win s520,000 with probability 61%, s0 otherwise LB : Win s500,000 with probability 63%, s0 otherwise

Out of these two, the decision maker selects lottery A. The decision maker is also given the choice between the following two lotteries:

LC : Win s520,000 with probability 98%, s0 otherwise LD : Win s500,000 with probability 100%, s0 otherwise

If the decision maker behaves according to expected utility, which option do they pick out of the second pair, given that they picked LA  out of the first? Why is this certain? Hint: suppose u($0) = 0.

3. There is a town with 100 identical residents, each with initial wealth of $1000 and a utility function for wealth given by u(x) = ,x. Every person owns a car and there is a probability p = .2 that a person’s car will need a costly repair in a given year. If a person needs a repair, they must pay $500 to fix it.

(a) What is the maximum amount that a single person would be willing to pay to insure against the cost of repairing their car?

 

(b)  Suppose a single company (e.g., a Monopoly) exists that can offer insur-ance policies. What price do they charge? What are its expected profits?

 

(c) Bonus: what is the probability that the insurance company incurs a loss in a given year? (for simplicity, assume i.i.d. damage)

 

4. A crude way to estimate your own utility. Consider the following lottery

 

L = 

 

,

$100

$0

p = 0.5

p = 0.5

 

(a) First,  do your best to figure out the sure amount  $c that makes you

indifferent between L and $c.  To do so, imagine you were asked if you would rather have $c or L, starting at c = 1 and increasing up to c = 50 (think about why we’re stopping at 50). Stop at the first number at which you prefer $c; this is your certainty equivalent. Report this number.

(b) Next, let’s assume a particular form for your utility. In particular, we will suppose u(x) = x1 −ρ for ρ 0, ρ  1. Since you are indifferent between $c and L, you know that they must have the same (expected) utility. Write out this equation.

(c) Now, solve for ρ.  Hint:  you will need to use the fact that ln(x1 −ρ ) = (1 .ρ) ln(x). Report ρ

(d)  Sketch the graph of your utility function. For help, you may go to https: //www.desmos.com/calculator/fzj4kn33ti and adjust the parameter to match your estimate.

(e) Finally, using your estimated utility function, let’s evaluate the following

hypothetical investment.  You have wealth w = $100, 000 and can invest

$10, 000 into a new venture. You estimate that there is a 30% chance of this investment yielding a profit of $25, 000, and a 70% chance of losing your investment.  That is, deciding whether make the investment or not is choosing between L1  = $100, 000 and

 

.(.) $125, 000   p = 0.3

,$90, 000     p = 0.7

Should you make this investment? Does your estimated utility accurately predict what you would choose?