Reducing Item Nonresponse to Vote-Choice Questions: Evidence from a Survey Experiment in Mexico.

Retrospective vote choice is a critical question asked in political science surveys. Yet, this question suffers from persistently high item nonresponse rates, which can bias estimates and limit scholars' ability to make sound inferences. In this paper, we develop a sensitive survey technique to decrease nonresponse to the vote-choice question in a representative, face-to-face survey in Mexico City and Mexico State in 2018–2019. Respondents received different iterations of three treatments: an anonymity guarantee, a confidentiality reminder, and audio-assisted interviewing technology. The use of audio technology combined with a credible anonymity guarantee significantly improved item response. Both anonymity and confidentiality assurances improved the accuracy of response, which more closely resembled official results in the treatment conditions. We then evaluate two non-rival mechanisms that might drive our findings: beliefs about response anonymity and re-engagement with the survey. We find that increased perceptions of response anonymity are associated with improved item response. [ABSTRACT FROM AUTHOR]