Michigan Social Pressure Voting Mailer
University of Michigan / Yale University · Michigan, USA · 2006
Summary
The Michigan social pressure experiment produced the largest voter mobilization effect ever documented in a randomized study — 8.1 percentage points from a single mailer. The mechanism was social accountability: seeing that neighbors' voting records would be disclosed before and after the election activated compliance with an implicit civic norm. The experiment is as important for what it raised as for what it found. The effect was so large that it prompted immediate ethical debate: is it appropriate for civic organizations to use social pressure in democratic participation? The experiment created a new subfield of political science, was replicated over 100 times, and directly changed how campaigns, parties, and nonpartisan organizations approach voter mobilization.
Research question
"Does showing voters their own voting history alongside their neighbors' records increase turnout in a low-salience primary election?"
Methodology
Intervention
344,084 registered voters randomly assigned to four groups: (1) civic duty message only, (2) Hawthorne message (you are being studied), (3) self-disclosure (your own voting record shown), (4) social pressure (your record plus neighbors' records shown, with implicit threat of follow-up disclosure). Control received no mailing.
Assignment
Randomized controlled trial (individual)
Sample size
344,084 registered voters
Primary outcome
Voter turnout in August 2006 Michigan primary election
Effect estimate
Social pressure arm: +8.1 percentage points vs. control; self-disclosure: +4.9 pp; Hawthorne: +2.5 pp; civic duty: +1.8 pp. Social pressure arm produced the largest GOTV effect ever recorded in a randomized study at that time.
Decision
Finding replicated in 100+ subsequent studies across multiple countries and election contexts; social pressure mailers became a standard tool in political campaigns and voter mobilization programs; raised significant ethical debate about use in civic contexts
Result
Positive
Social pressure arm: +8.1 percentage points vs. control; self-disclosure: +4.9 pp; Hawthorne: +2.5 pp; civic duty: +1.8 pp. Social pressure arm produced the largest GOTV effect ever recorded in a randomized study at that time.
Evidence strength
Strong
Randomized trial, replicated across multiple sites or studies.
Replication status
Replicated
Institution
University of Michigan / Yale University
Location
Michigan, USA
Year
2006
Policy area
Voter Engagement
Mechanism
Social norms