Ohio announced a Vax-a-Million Lottery in May 2021 to encourage people vaccinated. If people may avoid vaccination because (1) they worry about rare but critical side effects or (2) they want to free ride on herd immunity, the vaccination lottery may work better or worse than a lump-sum transfer...

Session-specific features of a laboratory experiment, if those exist, do not disappear by clustering standard errors at the session level. Randomly ordering sessions, which is crucial to deal with sampling issues, cannot justify clustering the standard errors at the session level. The...