Estimating Causal Effects of Ballot Order from a Randomized Natural Experiment: California Alphabet Lottery, 1978--2002

72 Public Opinion Quarterly 216

Daniel E. Ho & Kosuke Imai


Randomized natural experiments provide social scientists with rare opportunities to draw valid causal inferences in real world settings. We capitalize on such a unique experiment to examine how the name order of candidates on ballots affects election outcomes. Since 1975 California has randomized the ballot order for statewide offices with a complex alphabet lottery. Adapting statistical techniques to this California alphabet lottery, our analysis of statewide elections from 1982 to 2002 reveals that in general elections ballot order significantly impacts minor party candidates, while having undetectable effects on major party candidates. This result contradicts previous studies that find large and significant ballot order effects in general elections for major party candidates. In primaries, however, we confirm that being listed first benefits all parties. Major party candidates generally gain one to three percentage points, while minor party candidates may double their vote shares. In all races, the largest effects are for nonpartisan races where candidates in first position gain three percentage points.

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