Voter Mobilization via SMS: Evidence from a large-scale trial with language targeting. Brown bag session

Salomo Hirvonen, Postdoctoral Researcher, University of Turku

We conduct a large-scale get-out-the-vote short text-message (SMS) randomized controlled trial targeting the eligible voter population of Finland in 2025 municipal and county elections, with around 350,000 treated individuals.

First, consistent with earlier findings, we find a positive average treatment effect for young voters from receiving an SMS voting reminder signed by the official electoral authority. We show that the estimated effect is similar among the older voters. By merging treatment information with rich administrative data, we examine various forms of effect heterogeneity as well as within-household spillovers.

Second, among treated individuals whose registered mother tongue is one of the 22 most common non-native languages, we randomized whether they received the message in their own language. We find a positive statistically significant effect of receiving the message in one’s own language rather than in Finnish, with notable treatment-effect heterogeneities across language groups.