Boal's Econ

ECON 115 - Labor Economics
Drake University, Spring 2019
William M. Boal

EXAM 3 ANSWER KEY

Version A

I. Multiple choice

(1)d. (2)d. (3)b. (4)c. (5)b. (6)a. (7)c. (8)b. (9)c. (10)b. (11)d.

II. Problems

(1) [Measuring inequality: 15 pts]

Third Annual wage Share of earnings Cumulative share

Lowest $10 thousand 5 percent 5 percent

Middle $60 thousand 30 percent 35 percent

Highest $130 thousand 65 percent 100 percent
Lorenz curve passes through (33,5) and (67,35).
Gini = 0.400.
90-10 wage gap = 1200 percent.
90-50 wage gap = 116.7 percent.
50-10 wage gap = 500 percent.

Third	Annual wage	Share of earnings	Cumulative share
Lowest	$10 thousand	5 percent	5 percent
Middle	$60 thousand	30 percent	35 percent
Highest	$130 thousand	65 percent	100 percent

(2) [Shifts in relative supply and demand: 8 pts]

decrease.
1.425, because 1.6 = 2.28 / (percent change (W_C/W_H).
Relative demand for skilled workers must have shifted to the right even faster than relative supply did.

(3) [Joint migration decision: 8 pts]

NGM_A = $1,000,000 - $1,000,000 - $50,000 = $-50,000.
NGM_B = $1,200,000 - $800,000 - $50,000 = $350,000.
Total NGM = $300,000, so yes they will move to Los Angeles.
Party A is a tied mover, because NGM_A is negative, yet Party A will move.
Party B is neither, because NGM_B is positive, so wants to move.

(4) [Roy model: 6 pts]

Workers move if the net gain from migration is positive--that is, if w_Y > w_X + moving cost. Substituting and solving for S gives 70 < S.
Positively selected, since workers from the high end of the distribution of S in country X will move.

(5) [Immigration surplus: 8 pts]

$40 thousand.
$30 thousand.
$800 billion.
$100 billion.

(6) [Oaxaca decomposition: 6 pts]

Raw log wage differential is found by substituting each group's average schooling into its own wage equation, to give 2.9 - 2.3 = 0.60.
The log wage differential due to schooling equals the coefficient of schooling for green workers (who are not subject to discrimination) times the difference in average schooling = 0.12 (15-14) = 0.12.
The log wage differential due to discrimination is given by the difference in intercepts, plus the difference in slopes × blue workers' average schooling, or (1.1-0.9) + (0.12-0.10)14 = 0.48. Alternatively, the differential due to discrimination may be computed as the raw log wage differential minus the differential due to schooling.

(7) [Employer preference discrimination: 18 pts]

The firm that does not discriminate hires only blue workers because they are cheaper. Set VMP = price × MP_E = $10 and solve to get E_B = 36. Substitute into production function to get q = 180 units. Compute profit as total revenue minus labor cost to get $360.
This firm hires only blue workers because it perceives their wage as 10 (1+0.2) = $12, still cheaper than green workers. Set VMP = price × MP_E = $12 and solve to get E_B = 25. Substitute into production function to get q = 150 units. Compute profit as total revenue minus (true) labor cost to get $350.
This firm hires only green workers because it perceives blue workers' wage as 10 (1+1.5) = $25, more expensive than green workers. Set VMP = price × MP_E = $15 and solve to get E_G = 16. Substitute into production function to get q = 120 units. Compute profit as total revenue minus labor cost to get $240.

(8) [Monopsony wage discrimination: 12 pts] This is similar to problem (2) on Exam 2, but with two groups of workers.

MLC_G = 3 + (E_G /50). MLC_B = 1 + (E_B /25).
For each group, set VMP equal to MLC and solve for E. This gives E_G = 1100 and E_B = 600.
Substitute into supply equations to get w_G = $14 and w_B = $13.
If the minimum wage is lower than the efficient (or competitive) wage, then employment is determined by the supply curve. Here the minimum wage = $15 < efficient wage = $25. So substitute the minimum wage into the supply equation for each group and solve to get E_G = 1200 and E_B = 700.

III. Critical thinking

(1) According to Sherwin Rosen (1981), "superstars" are people who are slightly more able than their rivals, but manage to convert this slight difference into a huge difference in earnings by using technology to reach a mass audience (through publishing, electronic media, etc.)

A heart surgeon cannot be a "superstar" because a surgeon cannot use technology to reach a mass audience. A surgeon can only operate on one patient at a time.
A violinist can be a "superstar" because a violinist can reach a mass audience through recordings and broadcasting.

(2) We cannot conclude from the information given that immigrants double their earnings in 20 years because of possible cohort effects. To estimate the return to labor-market experience, we must follow the same cohort over time. Immigrants who have been here 10 years are likely different from immigrants who have been here 30 years--they come from different countries and likely had different amounts of human capital when they arrived. So to estimate the returns to experience, we must compare immigrants in the latest Census who have been here 30 years with immigrants in the Census 20 years earlier who had been here 10 years.

Version B