Beeps per Minute

How do peer preferences affect your own? Recently, this blog examined a paper by economists Michael Kremer and Dan Levy about the peer effects of alcohol use among college students (archived link here). The paper suggests that students who are randomly assigned to frequent-drinking roommates will, on average, earn a lower grade point average (GPA) than students matched with non-drinkers. According to the authors, students exposed to frequent-drinking roommates develop a strong taste for booze--a taste that sticks around and continues to lower their GPAs in the years after the roommate situation changes. More broadly, the paper suggests that peer consumption preferences may exert an eerily strong influence over our own. Economists also refer to this phenomenon as the "demonstration effect."

What about the peer effects of our coworkers? In his latest column, Tim Harford--the Undercover Economist--writes about research by UC Berkeley economists Alexander Mas and Enrico Moretti on the peer effect among supermarket clerks. How do checkout clerks change their behavior when an especially fast clerk joins their shift? Do they slack off as the faster clerk picks up more of the workload? Or does the presence of a faster worker encourage them to boost their effort? Read Harford's latest Slate column to find out more.

Discussion Questions

1. Productivity is the amount of output per unit of labor input. How do Mas and Moretti measure the productivity of supermarket clerks?

2. According to Mas and Moretti, the presence of a quicker clerk encourages the other clerks to work harder. What is the size of the peer effect?

3. Mas and Moretti are convinced that peer effects, not checkout-stand congestion or managerial decisions, explain the changes in productivity. What makes them so sure?

4. A clerk's productivity rises only when a particularly fast colleague is facing (watching) her. If a clerk is looking at the back of a particularly fast colleague, her productivity does not change. What does this say about our motivation to work harder in the presence of an especially productive coworker? Given this evidence, what effect do you think automated checkout stands have on the work habits of supermarket clerks?

5. Suppose you're an analyst for a major supermarket chain. Given the results of Mas and Moretti's research, how would you go about designing shifts of workers with different productivity levels in order to maximize the number of beeps (checked items) per minute?

To view the abstract of Mas and Moretti's research paper, click here.

College Drinking and GPA: 4.0 or Fewer?

In 1995, Christopher Buckley gave a speech at the Yale Daily News banquet. Afterwards, he wrote an angry op-ed in The New York Times called "Bombed in New Haven." Said Buckley at the time, "We knew how to party in my day, too." But:

The scene that greeted me in the dining room at the New Haven Lawn Club was out of a putsch in a Munich beer hall, minus the brown shirts and funny salutes. The leaders were bellowing so loudly that you had to shout to converse with your dinner partner. At one table, a fifth of vodka was being passed around and glugged from. At another table, a woman was slumped over her boyfriend, unconscious. Well, they had been drinking since 5 in the afternoon. Apparently the trend these days is to "front-load," that is, go to a party before the event and get so tanked that you will feel no pain later on. Or be aware that there is a guest speaker.

Of course, college students are used to being lectured about how excessive drinking is risky to one's health. According to economists Michael Kremer and Dan Levy, though, it may also be dangerous for one's GPA.

Kremer and Levy examined how alcohol use among college students affects academic performance. In short, they asked: What happens to a student's GPA if they are randomly assigned to a roommate who drinks? Read the abstract, introduction, and conclusions (skip the technical mid-section) of Kremer and Levy's research paper to find out. (Note that the authors get at a deeper economic question in the paper: Do peers influence the way people form consumption preferences?)

1. What happens to the college GPAs of young men who share dorm rooms with frequent drinkers? Is the effect stronger for male students at the top (high high-school GPA) or bottom (relatively low high-school GPA) of the GPA distribution?

2. What happens to the college GPA of a young man who drank frequently in high school when he is assigned to a dorm room with a fellow drinker?

3. How does the GPA effect of rooming with a drinker play out over time? Do Kremer and Levy find that the effect on GPA is stronger in the first year of college or in the second or subsequent years?

4. Do the authors find any evidence that a drinking roommate affects the college GPAs of young women?

5. Suppose a university establishes substance-free housing. How will this affect GPAs of students who self-select into the substance-free dorm rooms? What types of students will end up rooming together in the not-so-substance free dorms? How might such segregation impact the average GPA at the university?