Gerber, Green, and Larimer: Social Pressure and Voter Turnout: Evidence from a Large-Scale Field Experiment

Gerber, Alan S.; Green, Donald P.; Larimer, Christopher W. 2008. Social Pressure and Voter Turnout: Evidence from a Large-Scale Field Experiment. American Political Science Review 102 (February): 33-48.

Suppose that the government made a habit of sending your neighbors a letter after every election, telling them whether or not you had bothered to vote. Would you be more likely to turn out? Odds are that you would. At least, that's the conclusion of a massive experiment likely to change the way campaigns mobilize voters.

In an article by Gerber, Green, and Larimer, these three political scientists report the result of a large-scale randomized experiment involving 180,000 Michigan voters. You may not know it, but several states (including Michigan) make it a matter of public record whether or not you vote. Anybody willing to pay a small access fee can have a list of registered voters, including names, addresses, and turnout information.

Once you've got this information, designing an experiment is easy. First, find out who has voted in recent elections and who hasn't. Then, apply some sort of treatment to a randomly selected group of these people. Finally, observe turnout in a future election and see whether the treated group increased its turnout.

What the Researchers Did

That's the pattern the authors followed. They acquired this turnout information for 180,000 voters, then divided them into a control group (with 100,000 members) and four treatment groups (with 20,000 voters each). These five groups were all similar in terms of household size, gender balance, average age, and average turnout over the previous few elections. The general question was this: Can we come up with a "treatment" that will cause a treated group to vote at significantly higher levels than the untreated control group?

The four treatments were designed to play on our sense that voting is a civic duty. There's an internal and an external side to civic duty. The internal side represents the positive "warm fuzzies" that you might feel inside if you fulfill your duty by voting. The external side represents the negative social shame you might feel from others if you fail to vote.

Treatment #1 was a simple postcard with a gentle reminder to recipients that voting is a duty, so they should participate in the upcoming primary election. Treatment #2 added a note that researchers were watching this election to learn about turnout (to control for any Hawthorne effects). Treatment #3 removed this research note, but added a reminder "that who votes is a matter of public record," with the recipient's turnout behavior over the past couple elections written below; following was an ominous reminder that "we intend to mail you an updated chart" after the primary, indicating whether you voted.

Treatment #4 was the doozy. At the top, in capital letters, was the question, "What if your neighbors knew whether you voted?" After a brief explanation, the mailer displayed the turnout record for the recipient and all the recipient's neighbors. This is the sort of mailer that causes new cases of paranoid schizophrenia. If you're not picturing what this mailer would have looked like, take a look at this sample (from the article's appendix; click on the image to enlarge it):

Click to enlarge

What the Researchers Found

Treatment #1 yielded a turnout rate 1.8 percentage points higher than the control group's. Previous researchers have tried things similar to treatment #1 and found similar results. Treatment #2 raised turnout 2.5 points relative to the control. Treatment #3 raised it 4.9 relative to the control. These are large changes.

But treatment #4 raised turnout by a whopping 8.1 percentage points from the control.

Let's put that in perspective. In other experiments, the greatest boost in turnout came when experimenters sent door-to-door canvassers. The effect of these "social pressure" mailings was roughly the same as sending somebody to the voter's door. However, it was far more cost effective. Canvassing costs roughly $20 per vote, while these mailers cost roughly $1.93 per vote. Of course, that doesn't mean political consultants should jump on this new tactic; many recipients of treatment #4 called the number listed on the mailer to complain.

So what does this all mean?

It means two things. First, it means that there is a substantial internal "civic duty" motivation that gets people to vote. Sure, they might vote because they care about the outcome, or because they think their vote matters for the outcome. But (as treatment #1 shows) they also vote because they want the internal "warm fuzzies" of voting.

Second, there is an even stronger external "civic duty" motivation. Social shame matters, and in a big way. This sense of (external) civic duty gets activated when people know that others can observe their behavior. Shame works. The authors seem almost surprised by this finding. The psychological and sociological literatures warn of "reactance" when heavy-handed tactics are used to enforce norm compliance--so the authors seem to have half expected turnout to fall among group #4. But instead of reactance, they saw a large rise in compliance.

Most precincts give out those little "I voted" stickers to encourage people to vote, presumably to tap into these social rewards. If we really want to improve turnout, maybe the government should start mailing out postcards similar to treatment #4 before (and after) every election!