Field Experiments Testing the Impact of Radio Advertisements on Electoral Competition

Localities in treatment municipalities were exposed to 60 seconds of a non-partisan get-out-the-vote radio advertisement which urged voter to vote on Election Day, included the names, incumbency status, and party affiliations (where applicable) of the main candidates in each race. The announcement made no evaluative remarks about the candidates. The size of the announcement was varied in each municipality so that cities or towns were exposed to 50, 70, or 90 gross ratings points (GRPs) of radio advertising. Treatment cities whose cost-per-point was less than $30were treated with 90 GRPs. Treatment cities whose cost-per-point was greater than $30 but less than $40 were treated with 70 GRPs. All other treatment cities received 50 GRPs. The statistical analysis controls for the volume of GRPs.

2005-11-01

2006-11-06

Electoral competitiveness

The difference between the vote percentage won by the incumbent in 2005 or 2006 and his or her vote percentage in the previous election.

Of the nation’s 1,183 cities and towns, places with populations of over 30,000 and where cost for radio advertisements was below $111 per point were shortlisted. The 151 shortlisted municipalities were matched into pairs based on criteria thought to affect election competitiveness. These matching criteria were voter turnout and incumbent vote share in the previous mayoral election, whether mayoral elections are partisan or nonpartisan, and whether the 2005 mayoral election was contested. This resulted in 28 pairs of cities with one of each pair randomly assigned to control and the other to treatment. From these, 33 municipalities (16 treatment and 17 control) where an incumbent mayor was running opposed were selected as sample cities. The radio advertisement was played in treatment cities only.

In November 2006, 105 municipalities held mayoral elections. Using the process as in 2005, 11 pairs of municipalities were created, half of which were randomly assigned to the treatment group. Of these, 16 cities—seven in the treatment group and nine in the control group—featured elections in which incumbent mayors ran opposed in 2006.

Matching pairs and random assignment done in office by computer.

Municipality

No

Study not clustered

49 municipaities

Treatment: 23 municipalities
Control: 26 municipalities

FIELD EXPERIMENTS TESTING THE IMPACT OF RADIO ADVERTISEMENTS ON ELECTORAL COMPETITION

Results from previous studies of campaign spending imply that equal-sized grants to both incumbents and challengers are a net benefit to challengers, who on average spend less money and derive greater marginal returns from each additional dollar. This study provides an experimental test of this proposition. Cities holding mayoral elections in November 2005 and 2006 were randomly assigned to broadcast nonpartisan radio ads that stated the names of the mayoral candidates, reminded listeners about the date of the upcoming election, and encouraged them to vote. Consistent with the findings of previous studies on the differential effects of incumbent and challenger campaign spending on election outcomes, we find that these radio ads produced substantially more competitive elections. The borderline statistical significance of our results, however, invites replication of this experiment.

Panagopoulos, Costas, and Donald P. Green. 2008. "Field Experiments Testing the Impact of Radio Advertisements on Electoral Competition." American Journal of Political Science 52(1): 156–168.

http://onlinelibrary.wiley.com/doi/10.1111/j.1540-5907.2007.00305.x/pdf