Randomization Method
Based on tax data, the project partner classified tax households as potentially eligible or ineligible for health insurance subsidies. Our unit of observation is the tax households that may consist of single individuals, married couples with or without underage children, or adult children. Consequently, a residential household, defined by the living unit, such as an apartment or house, can encompass multiple distinct tax households. Residential households are defined based on Swiss federal building and apartment identifiers (i.e., EGID, EWID). We cluster the treatments on these residential households to reduce spillovers.
After the eligibility and treatment clusters are defined, two steps are required to obtain the experimental groups: (i) sample restriction and (ii) group assignment. First, the study population is restricted to residential households, where no one has applied online in the last year. Clusters with previous experience with the online application are excluded from the experimental sample. Second, treatment clusters with tax households that are newly eligible in this year, have never applied before, or everyone has previously applied with the paper application will be randomly assigned to one of the two experimental groups with equal probability.
The randomization will be conducted by the research team, using the software R. We will then send the assigned treatment indicators to the social insurance office. These groups are then used to create batches that are sequentially forwarded for printing. The envelopes include letters informing tax households about their potential eligibility and how they can apply. The envelopes are assembled within these treatment batches to prevent mistakes. However, everything will be dispatched on the same day.