Social preferences are stable over long periods of time
基于2005至2011年对越南农村同一非学生样本的四次观测，发现人们在真实公共品（如桥梁）和公共品博弈中的自愿贡献高度相关，表明亲社会偏好长期稳定。
We measure people's pro-social behavior, in terms of voluntary money and labor contributions to an archetypical public good, a bridge, and in terms of voluntary money contributions in a public good game, using the same non-student sample in rural Vietnam at four different points in time from 2005 to 2011. Two of the observed events are actual voluntary contributions (one in terms of money and one in terms of labor), one is from a natural field experiment, and one is from an artefactual field experiment. Despite large contextual variations, we find a strong positive and statistically significant correlation between voluntary contributions, whether correcting for other covariates or not. This suggests that pro-social preferences are fairly stable over long periods of time and contexts.