Over-Time State and National Bias in CCES Vote Validated Turnout Rates

Inspired in part by a Grimmer et al. (2018) research note that touches on CCES turnout data usage, I calculated turnout bias at the state level in every election that the CCES covers (from 2006 to 2016). I measure bias as the difference between the vote validated state-level turnout from the CCES (survey turnout) and the voter eligible population (VEP) for highest office turnout taken from the United States Election Project (actual turnout). Positive values indicate survey overestimates of turnout, while negative values indicate underestimates. I break up the state-level measures of bias by region to make the visualization clearer, and at national level bias appears at the end.

Results here generally shed light on the reliability of state-level turnout measures generated from the CCES, especially in the context of the research that Grimmer et al. discuss (over time turnout comparisons across state). The data here also reflects the quality of state-level voter files and the ability of the CCES to match its respondents to each state’s voter file. Aside from a few cases, certain states are generally not consistently less biased than others over the last six elections. Bias across states is also pretty volatile and changes a good amount from election year to election year. At first glance, there does not appear to be a pattern to cross-state and across time turnout bias in the CCES.






Over-Time State and National Bias in CCES Vote Validated Turnout Rates

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