The Effect of Prepaid Postage on Turnout: A Cautionary Tale for Election Administrators

Researchers randomly provided postage-paid envelopes to a subset of permanent absentee voters in San Mateo County, California in order to evaluate its impact on voter turnout. Treatment-group individuals were sent a postage paid envelope with their absentee ballot. In addition, individuals also received an insert with voting instructions. The front sides of both treatment and control inserts were identical but the instructions on the back of the inserts sent to the treatment group voters noted that postage was not required, while control group voters were provided standard instructions. The prepaid envelopes and appropriate instruction sheets were inserted into the ballot mailings and were sent out in the same manner as the control-group ballots.

2010-01-01

2010-11-01

1) Voter turnout
2) Method of voting if any (abstain, in person, by mail)

After Election Day, researchers obtained an updated voter file from the San Mateo County Registrar of Voters, which provided validated turnout information for individuals in treatment and control groups. San Mateo County records whether each voter cast a ballot by mail, in person on Election Day, or in person during the early voting period.

From a list of 148,000 registered permanent absentee voters in San Mateo County, 10000 were randomly selected to be in the treatment group. Assignment of voters to the treatment was clustered by household. In other words, all voters registered at the same address received the same set of voting instructions so that people in the same household were not exposed to different treatments. Treatment voters received postage paid envelopes with their mailed in ballot while control voters received the usual envelopes with their ballot. Voting records for both control and treatment groups were collected from the Registrar of Voters.

By computer

Household (voters registered at the same address received the same set of voting instructions)

Yes

99,214

148,840 permanent absentee voters

Treatment: 10,000 permanent absentee voters
Control: 138,840 permanent absentee voters

THE EFFECT OF PREPAID POSTAGE ON TURNOUT: A CAUTIONARY TALE FOR ELECTION ADMINISTRATORS

In collaboration with local election officials, we conducted a randomized field experiment in which postage-paid envelopes were provided to a random sample of 10,000 permanent vote-by-mail (VBM) voters in San Mateo County, California, in advance of the November 2, 2010, general election. We find that the treatment generated statistically significant but unexpected effects: postage-paid envelopes increased the probability that voters cast their ballots in person and decreased the probability that they cast their ballots by mail. These offsetting effects meant that the intervention produced no net change in voter turnout. We find that this pattern of countervailing effects is strongest among voters who frequently voted by mail in the past, those potentially most susceptible to disruptions in routine. Post-election interviews support the idea that the postage-paid envelopes created confusion for some voters. The results suggest that reforms designed to increase turnout by decreasing voting costs may have the unintended effect of disrupting routines.

: Michelson, Melissa R., Neil Malhotra, Andrew Healy, Donald P. Green, Allison Carnegie, and Ali Adam Valenzuela. 2012. "The Effect of Prepaid Postage on Voter Turnout: A Cautionary Tale for Election Administrators." Election Law Journal 11(3): 279-290.

http://online.liebertpub.com/doi/abs/10.1089/elj.2012.0150