All Japanese are covered by the social insurance system. Following the claim issued by hospitals and clinics, the insures pay the remuneration for the diagnosis and treatment excluding the copayment directly paid by the patient. The claim data has much useful information on the patient, such as age and gender, inpatient or outpatient status, and the fee for service. Over 50 million observations of claim data of the National Insurance System including 4 prefectures during 1997 fiscal year, were used to generate descriptive statistics and to analyze the effects of the copayment change introduced in Sept. 1997.
