Are more children better than one? Evidence from a lab experiment of decision making

Abstract This paper examines the impacts of siblings on people's social preference, risk attitude and time preference with a data set from a large-scale lab experiment. Employing the variation of fine rates under One-Child Policy for excess birth in different regions as instrument to address the endogeneity of whether having siblings, we find that sibling's role mainly focuses on shaping people's social preference that subjects with siblings demand less as responders in ultimatum game and behave more cooperatively in sequential prisoner's dilemma. This conclusion survives through several robustness checks. Our further result suggests that more sibling interactions and less parental expectations are two potential mechanisms through which siblings play a role in making people more prosocial. Our findings point to a positive externality along with Two-Child Policy which is widely neglected in both policy evaluation and relevant theory such as quantity-quality theory, and provide implications for the fertility policy such as the recent Three-Child Policy in China and beyond.