QUESTION 1

1. [70 MARKS] Consider the following simplified version of the paper “Self-Control at Work”

by Supreet Kaur, Michael Kremer and Sendhil Mullainathan (2015). In period 1 you will

perform a number of data entry task for an employer. The effort cost of completing x

tasks is given by αx2

, where α > 0. In period 2, you will be paid according to how many

task you have done. The (undiscounted) utility for receiving an amount of money y is

equal to y. From the point of view of period 1, the utility from completing x tasks and

getting money y is equal to

−αx2 + βy

where β ∈ [0, 1], while from the point of view of period 0 it is

−αx2 + y.

Assume that you are not resticted to completing whole number of tasks (so you can solve

this problem using derivatives).

(a) [15 MARKS] Assume that you get paid $1 for each task (so if you complete x tasks

you get y = x). In period 1, you are free to choose how much work to do. Calculate

how much you will find optimal to do (as a function of α and β).

(b) [15 MARKS] Derive how much work you would choose to do if you could fix in

period 0 the number of tasks you would do in period 1 (as a function of α). Call this

x

∗

(α) (the number of task completed under commitment). Assuming β < 1, show
whether x
∗
(α) is higher or lower than the effort level you would choose in period 1
for the same α. Interpret your results.
(c) [15 MARKS] Assume that α = 1 and β = 1/2 and that you are sophisticated, i.e.
you know that the number of tasks you plan at period 0 to do in period 1 is higher
than what you will actually choose to do in period 1. Derive how much of your
earnings you would be prepared to pay to commit to your preferred effort level in
period 0. i.e. calculate the largest amount T that you would be prepared to pay such
that you would prefer to fix effort at x
∗
(1) but only receive x
∗
(1) − T in payment,
rather than allow your period 1 self to choose effort levels.
(d) [20 MARKS] Self-Control problem does not only affect you, but also the employer
who you work for and who wants all the tasks to be completed. As a result, both you
and the employer have self-interest in the provision of commitment devices. In what
follows, we investigate the provision of commitment by the employer, considering a
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different wage scheme. In this wage contract you only get paid x if you complete at
least as many tasks in period 1 as you would want in period 0, x ≥ x
∗
(1). Your pay,
however, will only be λx (with λ < 1) if you complete fewer task in period 1 than
what you find optimal in period 0, x < x∗
(1).
Show that if λ = 0 (commitment contract) then in period 1 you will choose to
produce x
∗
(1) if β ≥
1
2
, but not otherwise (still assuming α = 1).
Show also that this implies that if β =
3
4
, then in period 0 you would prefer the work
contract in which λ = 0 to the work contract in which λ = 1 (standard contract).
(e) [5 MARKS] Now again assume that β =
3
4
. Using your results above, calculate how
much you would choose to work in period 1 if
• α = 1 and λ = 0
• α = 1 and λ = 1
• α = 2 and λ = 1
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QUESTION 2
2. [30 MARKS] Consider the paper “Myopic Loss Aversion and the Equity Premium Puzzle”
by Shlomo Benartzi and Richard H. Thaler (1995).
(a) [5 MARKS] Explain shortly what the equity premium puzzle is.
(b) [5 MARKS] The authors explain the equity premium puzzle by using two concepts,
the concept of loss aversion and mental accounting. Explain what loss aversion is
and how it is related to prospect theory. Explain what mental accounting is.
(c) [5 MARKS] As in the paper, consider the following simple utility function capturing
loss aversion, where x is a change in wealth relative to the status quo.
U(x) = (
x if x ≥ 0
2.8x if x < 0
(1)
Argue why you would or why you would not accept a bet where you win $100 with
50% probability, while lose $50 with 50%.
(d) [5 MARKS] Focusing on mental accounting, now assume that you are offered two
of the bet described in Question 2 (c), which are sequentially played out (but you
do not watch the bet being played out). Argue why you would or you would not
accept the bet now.[Hint: First calculate the distribution of outcomes (outcomes
with probabilities) created by the portfolio of two bets and then evaluate the utility
function!]
(e) [5 MARKS] Explain whether and why your answers to questions (c) and (d) would
change if the bet is the same as before, but now your reference point changes to
-$50.
(f) [5 MARKS] Explain what the examples in Question 2 (c) and 2 (d) imply for the
relationship between loss aversion and the frequency of performance evaluation.
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