We use a combination of two natural experiments and one field experiment tomeasure
people’s prosocial behavior in terms of voluntary money and labor time contributions to an
archetypicalpublic good-a bridge-in rural Vietnam, at three different points in time from
2005 to 2010. Since the experiments are far apart in time, potentially confounding effects of
moral licensing and moral cleansing are presumably small, if at all existent. We find a strong
positive and statistically significant correlation between voluntary contributions in these
experiments, whether correcting for other covariates or not.This result suggests that prosocial
preferences are at least partly stable over long periods of time.