This research examines the effects of vote-by-mail policies on ballot roll-off, or down-ballot voting. In examining data from Washington state, a state that first introduced no-excuse mail voting in the 1970s and gradually implemented vote-by-mail statewide, it appears voters who are given more time to study the candidates and issues are more knowledgeable and therefore have greater ballot completion rates (e.g. less ballot roll-off).
Analysis of voter turnout in the 2014 midterm election in Colorado shows that low-propensity voters, including young voters, significantly overperformed their predicted turnout levels. This report also contains analyses of predicted versus actual turnout among various subgroups, including those based on demographics, partisanship, and vote history. While not conclusive, the evidence generated by these analyses supports the assertion that Colorado’s universal vote-by-mail system — which debuted in 2014 — likely played a role in increasing turnout.
In this paper that examines the effects of prepaid postage on voter turnout in the Swiss Canton of Berne, researchers find that prepaid postage is associated with a statistically significant 1.8 percentage point increase in voter turnout. Overall, this amounts to 4 percent more voters participating.