The early bird catches the worm? School entry cutoff and the timing of births

Does the cutoff date for school entry affect the timing of births? Using administrative data from birth certificates that covers over five million newborns in Guangdong Province of China from 2014 to 2016, we find that more than 2000 births in a single year are shifted from seven days after the cutoff date to seven days before the cutoff date. Because of the strict administrative procedures in China to record births, manipulation of reported birthdates is infeasible. We also find evidence that mother and child characteristics systematically differ across the threshold; in particular, advantaged mothers are more likely to bring delivery forward to send their children to school at a relatively young age. These heterogeneous responses around the cutoff date violate the assumption in regression discontinuity design that the date of birth is exogenous. Moreover, our results contribute crucially to understanding the different starting age effects between China and developed countries.