This paper examines how health care utilization among low-income children is affected by a reduction of the coinsurance rate, exploiting an institutional change in the Medical Subsidy for Children and Infants (MSCI) system, as a natural experiment. In 2004, the maximum age for MSCI recipients in Hokkaido Prefecture was raised from 3 years to include all children of preschool age. The implied arc price elasticity of outpatient care utilization is −0.23, which is congruent with the commonly cited value (−0.2) presented in the RAND health insurance experiment
