David Cottrell, Michael Herron, and Dan Smith have posted this new draft. Here is the abstract:

Although most ballots in the United States have historically been cast in-person, an increasing number of Americans are turning to mail-in voting during the ongoing COVID-19 pandemic. Voters inexperienced with the form of voting, however, disproportionately submit ballots that end up being rejected, either because they arrive late at local elections offices or have signature defects on their return envelopes. Our analysis of ballot rejections in the political battleground state of Florida shows that inexperienced mail voters were three and 2.75 times more likely, respectively, in the 2016 and 2018 General Elections to have their ballots rejected than experienced mail voters. Similarly, in Florida’s recent 2020 Presidential Preference Primary, held in March 2020 as the COVID-19 pandemic was beginning to take hold in the state, voters inexperienced with mail ballots suffered from rejection rates 2.75 times as great as voters with experience voting by mail. Moreover, the effect of inexperience on vote-by-mail ballot rejection rates varies by party affiliation, race/ethnicity, age, and gender.