When Medicare was established in 1965, Congress adopted the private health insurance sector's "retrospective cost-based reimbursement" system to pay for hospital services. Under this system, Medicare made interim payments to hospitals throughout the hospital's fiscal year. At the end of the fiscal year, the hospital filed a cost report and the interim payments were reconciled with "allowable costs" which were defined in regulation and policy. Medicare's hospital costs under this payment system increased dramatically; between 1967 and 1983, costs rose from $3 billion to $37 billion annually.