Uncommon knowledge

What teachers unions really do

Surprising insights from the social sciences

By Kevin Lewis
March 13, 2011

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The recent wave of Republican political victories has turned the spotlight on public-sector unions. While there is plenty of rhetoric to go around, there doesn’t seem to be as much consideration of the effect that public-sector unions really have, one way or the other. In a unique natural experiment, New Mexico did not renew its mandatory collective bargaining law for public schools from 1999 to 2003, allowing a comparison of outcomes there over time and against other states. The analysis found that collective bargaining increased SAT scores and decreased graduation rates, with no overall effect on spending per student. This suggests that mandatory bargaining helps high-achieving students at the expense of low-achieving students. One reason for this, the authors offer, is that many collective bargaining agreements restrict the ability of administrators to transfer good teachers from high-achieving schools to low-achieving schools.

Lindy, B., “The Impact of Teacher Collective Bargaining Laws on Student Achievement: Evidence from a New Mexico Natural Experiment,” Yale Law Journal (March 2011).

Friending for profit Friends mind each other’s business. That’s the conclusion of a new study of graduates from Harvard Business School. Since 1949, new students at Harvard Business School have been randomly assigned to classroom sections, groups of students who spend most of their time together during their first year. Among alumni who went on to become top executives at S&P 1500 companies, section-mates were more likely to have entered the same industries, worked in the same locations, have more similar compensation, and follow more similar acquisition strategies than classmates who were not in the same section. Executive compensation and acquisitions become even more similar among section-mates in the year following a class reunion. It’s networking at work.

Shue, K., “Executive Networks and Firm Policies: Evidence from the Random Assignment of MBA Peers,” Harvard University (February 2011).

How smell shapes a decision Who needs sex education when you can use stink bombs? Students at the University of New Mexico entered a room to fill out a survey asking them about their intentions to purchase and use condoms over the next six months. Unbeknownst to the students, the researchers had sprayed a stinky liquid on the wall of the room. Compared to students who filled out the survey in a fresh-smelling room, students in the stinky room were more eager to use condoms. The effect of the spray was even stronger than the effect of the students’ own preexisting attitudes about condom use.

Tybur, J. et al., “Smells Like Safe Sex: Olfactory Pathogen Primes Increase Intentions to Use Condoms,” Psychological Science (forthcoming).

Weak arguments backfire No news is good news — or at least better than feeble news. Making a weak argument in favor of a prediction can make people more skeptical of that prediction than not making any argument at all. For example, when people were asked to consider betting on whether the Republicans would retake the House of Representatives in last year’s mid-term elections, they were half as likely to take the bet if told about a Republican who got an important newspaper endorsement in a hotly contested race. In other words, information that should’ve bolstered people’s confidence in the outcome — albeit marginally — instead caused people to pull back.

Fernbach, P. et al., “When Good Evidence Goes Bad: The Weak Evidence Effect in Judgment and Decision-Making,” Cognition (forthcoming).

Everything’s worth more when you relax Memo to the sales staff: Get your customers to relax. In a series of experiments, researchers found that induced relaxation — by watching a relaxing video or listening to relaxing music — increased the perceived value of various products. This happens because when people relax, they tend to think more generally about the value of a product, instead of focusing on the details. Relaxation did not increase perceived value if people were asked to think about specific aspects of the product or if they were put in a detail-oriented state of mind.

Pham, M. et al., “Relaxation Increases Monetary Valuations,” Journal of Marketing Research (forthcoming).

Kevin Lewis is an Ideas columnist. He can be reached at