Field Experiments Testing the Impact of Radio Advertisements on Electoral Competition
Last registered on May 11, 2016

Pre-Trial

Trial Information
General Information
Title
Field Experiments Testing the Impact of Radio Advertisements on Electoral Competition
RCT ID
AEARCTR-0001235
Initial registration date
May 11, 2016
Last updated
May 11, 2016 4:39 PM EDT
Location(s)
Primary Investigator
Affiliation
Fordham University
Other Primary Investigator(s)
PI Affiliation
Department of Political Science, Columbia University
Additional Trial Information
Status
Completed
Start date
2005-11-01
End date
2006-11-06
Secondary IDs
Abstract
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.
External Link(s)
Registration Citation
Citation
Green, Donald and Costas Panagopoulos. 2016. "Field Experiments Testing the Impact of Radio Advertisements on Electoral Competition." AEA RCT Registry. May 11. https://www.socialscienceregistry.org/trials/1235/history/8162
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Experimental Details
Interventions
Intervention(s)
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.
Intervention Start Date
2005-11-01
Intervention End Date
2006-11-06
Primary Outcomes
Primary Outcomes (end points)
Electoral competitiveness
Primary Outcomes (explanation)
The difference between the vote percentage won by the incumbent in 2005 or 2006 and his or her vote percentage in the previous election.
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
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.
Experimental Design Details
Randomization Method
Matching pairs and random assignment done in office by computer.
Randomization Unit
Municipality
Was the treatment clustered?
No
Experiment Characteristics
Sample size: planned number of clusters
Study not clustered
Sample size: planned number of observations
49 municipaities
Sample size (or number of clusters) by treatment arms
Treatment: 23 municipalities
Control: 26 municipalities
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB
INSTITUTIONAL REVIEW BOARDS (IRBs)
IRB Name
IRB Approval Date
IRB Approval Number
Post-Trial
Post Trial Information
Study Withdrawal
Intervention
Is the intervention completed?
Yes
Intervention Completion Date
November 06, 2006, 12:00 AM +00:00
Is data collection complete?
Yes
Data Collection Completion Date
November 06, 2006, 12:00 AM +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
Study not clustered.
Was attrition correlated with treatment status?
No
Final Sample Size: Total Number of Observations
49 municipalities.
Final Sample Size (or Number of Clusters) by Treatment Arms
Treatment: 23 municipalities Control: 26 municipalities
Data Publication
Data Publication
Is public data available?
Yes
Program Files
Program Files
Yes
Reports and Papers
Preliminary Reports
Relevant Papers
Abstract
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.
Citation
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.