Vote-by-mail categorization for 2018

To categorize states for the vote-by-mail analysis, researchers used the Census Bureau’s 2018 Current Population Survey Voting and Registration Supplement data. This data was accessed through CPS IPUMS database and contains information on the share of votes cast in person on Election Day, the percentage of votes cast in-person before Election Day, as well as the percentage of votes cast by mail.

States where 31% or more of voters cast ballots by mail in the 2018 midterm elections were categorized as “high” vote-by-mail states.

States where 10%-30% of voters cast ballots by mail were categorized as “medium,” and states where 0%-9% of voters cast ballots by mail were categorized as “low.”