Data resource profile: the Korea National Health Insurance Medical Expenditure Survey

The Korea National Health Insurance Medical Expenditure Survey (KNHI-MES) is an approved national statistical survey of total healthcare expenditure, including non-covered medical expenses paid entirely by patients, among individuals receiving care across 11 provider types in South Korea. Its primary purpose is to calculate the National Health Insurance (NHI) coverage rate: the proportion of total medical expenditure for therapeutic-purpose care paid through NHI benefits. This rate provides the primary evidence base for NHI policy development. Conducted annually since 2005, the survey uses stratified cluster sampling with 27 strata defined by provider type, billing volume, and specialty. In 2024, 2,961 providers were sampled from a frame of 99,773. Each billing record includes patient administrative variables and 3 cost components: payments reimbursed by the National Health Insurance Service (NHIS) to the facility for insured services, statutory patient co-payments for covered services, and non-covered medical expenses paid entirely by patients. Results are published in the annual KNHI-MES report, on the NHIS website, and through the Korean Statistical Information Service. This data profile describes the survey design, estimation methodology, and uses of the data resource.