This paper examines an unintended response to the One-Child Policy in China: twinning births. Analysis of population census data shows that the One-Child Policy has accounted for more than one-third of the increase in the reported births of twins since the 1970s. Investigation using birth space with prior births and height difference within twins suggests that the increase in births of twins is partly due to parents reporting regularly-spaced children as twins to avoid the policy violation punishment. The study highlights the possibility of individual behavioral response to undesirable government policies and the potential social consequences.

JEL Codes: J08, J11, J13;

Keywords: Twins, One-Child Policy, China