The health insurance system

Korea has a single public insurer, the National Health Insurance Service (NHIS), which covers almost the entire population. Coverage became universal in 1989, and the many separate insurance societies were merged into a single insurer in 2000. Because every resident is enrolled with the same insurer, the NHIS data follow people across jobs, regions, and providers without the gaps that arise when people switch insurers.

Who is covered

The population falls into six groups, and the group a person belongs to determines how their premium is set and how they appear in the data.

• Employee insured (직장가입자) are wage workers and their employers, who pay premiums based on wages. A business owner with at least one employee is an employee insured, while an owner without employees is a self-employed insured.
• Dependents of employee insured (직장피부양자) are family members of employee insured who meet income and property conditions, and who pay no premium of their own.
• Self-employed heads of household (지역세대주) head the households of everyone not covered as an employee insured, as a dependent, or by Medical Aid. These households are self-employed insured (지역가입자), and their premium is set for the household as a whole, based on its income and property.
• Self-employed household members (지역세대원) are the other members of these households, whose income and property count toward the household premium.
• Medical Aid heads of household (의료급여세대주) head low-income households that are covered by Medical Aid (의료급여) rather than health insurance, and pay no premium.
• Medical Aid household members (의료급여세대원) are the other members of these households.

Medical Aid is financed by the government and has its own cost-sharing rules, but its beneficiaries also appear in the NHIS eligibility data. The six groups are the codes of the insurance type variable in the eligibility tables, such as GAIBJA_TYPE (건강보험 가입자격 구분, insurance type) in the National Sample Cohort.

Benefits and cost sharing

Services are divided into covered services (급여), which are billed to the insurer with patient cost sharing, and non-covered services (비급여), which patients pay for entirely out of pocket. Only covered services are billed to the insurer, so non-covered services do not appear in the claims data. This matters for any measure of total spending, since the share of non-covered services varies across conditions, provider types, and years.

The NHIS and HIRA

Two public agencies handle claims, and both release research data. Providers submit claims to the Health Insurance Review and Assessment Service (HIRA, 건강보험심사평가원), which reviews them and passes the decisions to the NHIS for payment. The two agencies therefore hold overlapping claims records, but only the NHIS holds enrollment, premium, health screening, and linked death records.

	NHIS	HIRA
Role	Insurer, collects premiums and pays providers	Reviews claims and assesses quality of care
Enrollment and premium data	Yes	No
Health screening results	Yes	No
Death records	Linked from Statistics Korea	No
Claims	Yes	Yes

Health screening

The NHIS runs the national health screening program (국가건강검진), and screening results are available in several research databases. Most adults are invited for a general health screening every two years, while non-office workers are screened every year, and separate programs cover cancer screening and infants and children.

Long-term care

The NHIS also administers long-term care insurance for older adults (노인장기요양보험), introduced in July 2008.