Blog Post

AEIdeas

A new research paper out of the Massachusetts Institute of Technology (MIT) and Stanford University has attracted a lot of attention because the authors claim that college students value pizza more than their friends’ privacy. Here are some of the headlines about the paper, which was released as a working paper of the National Bureau of Economic Research (NBER):

But there’s a problem. The authors are wrong.

What does their research really show? People might be willing to be helpful if they are paid. And people have limited time and energy. Somewhere, Adam Smith is smiling.

What was the research about?

The paper is based on data from another study, one designed to investigate how students might use Bitcoin. The researchers conducting that study asked students to make choices about providing email addresses of friends to the researchers and about the types of security and privacy the students wanted with their Bitcoin.

The authors of the NBER paper use the study data to investigate students’ privacy preferences. But the authors appear to misinterpret what the students were doing.

Did students give up friends’ email addresses in exchange for a pizza?

No. Here’s what happened. About half of the research subjects were told: “List 3 friends you would like to share pizza with. One pizza will be on us! If you happen to talk about Bitcoin, even better!” The form asked for MIT email addresses, but not names. About 97.5 percent of the students provided accurate email addresses.

The other half of the students were told: “List 5 friends you would like to know the public addresses of. We will email you with addresses if they sign up for the directory.” (A Bitcoin address is a possible destination for a Bitcoin payment.) Again the form asked for MIT email addresses, but not names. About 95 percent of the students complied with accurate email addresses.

The paper’s authors conclude that (1) the questions were all about privacy and (2) the 2.5 percentage point difference between pizza group and the Bitcoin address group was all about pizza. The headline from Stanford University’s news service reflected these beliefs: “Pizza over privacy? Stanford economist examines a paradox of the digital age.”

What’s wrong with the authors’ conclusion?

There are several problems. One problem is that MIT email addresses aren’t private: They are available on the MIT website. Most students probably knew that, and the authors certainly did: They admit in the paper that they themselves used the MIT website to verify email addresses.

Because the students probably knew the email addresses were publicly available, it is unlikely that their choice of whether to write the email addresses was based on privacy concerns. The authors should have realized this because their statistics show no significant correlation between students’ stated attitudes toward privacy and their choices about writing email addresses.

Another problem is that the two groups of students were asked different questions related to email addresses: One was about pizza, and the other was about Bitcoin addresses. So the differences in students’ choices are the result of all the differences between the questions, not just pizza. For example, it is possible that students are more likely to want to share pizza than to immediately come up with five friends with whom they wanted to exchange Bitcoin.

Another possible explanation of the difference between the two groups is that some students might have thought that by writing down the email addresses, they were saving the researchers work. It is well known in marketing that if you do something for someone (such as give them pizza), then they will feel obligated to do something for you (such as write down email addresses). So the pizza likely served as a pretty good wage for writing down three email addresses.

What if the authors are right that it is all about privacy and pizza?

Even if all of the problems listed above didn’t exist, there is the problem that 95 percent of the students gave friends’ email addresses to the research team without any inducement at all. The pizza, if it mattered, made less than a 3 percent difference. That difference may be statistically significant, as the authors state, but it is hardly economically significant.

The bottom line? It is highly unlikely that students violated their friends’ privacy in exchange for a pizza. It is more likely that students receiving a pizza felt obligated to carefully write down three email addresses.