Who actually writes supplemental health insurance?

Method and limits

• Line mapping. Hospital indemnity = NAIC "Other Medical (Non-Comprehensive)", which also includes hospital-only, surgical, outpatient indemnity, ICU and transplant policies. Critical illness = "Specified/Named Disease", which also includes cancer-only policies. Accident = "Accident Only or AD&D", which mixes supplemental accident with group AD&D sold next to group life.
• Hospital indemnity is individual-only. The NAIC has no group line for it; group hospital indemnity sits inside "Other group care" with unrelated products, so the large worksite market is not visible here.
• Coverage. Only filers with state insurance departments. Self-insured employer plans and California DMHC-regulated plans are excluded.
• Premiums are direct earned, before reinsurance. Loss ratio = (incurred claims + change in contract reserves) / premiums earned, as reported. Rows under $1M of premium show "n/m": their loss ratios swing wildly.
• Loss ratio is not margin. Commissions, administration and premium taxes come out of the remaining premium. Use the viability check to model that.
• Shares use the NAIC-reported segment total as the denominator. Listed rows can sum slightly above 100% because negative-premium filers are in the total but not listed.
• Concentration (HHI) = sum of squared shares (in %) of the listed groups. Bands follow the 2023 DOJ/FTC Merger Guidelines: above 1,800 is highly concentrated, 1,000–1,800 moderately, below 1,000 unconcentrated.
• Groups are the NAIC group structure as of the report date (September 2025); later M&A is not reflected.

Sources

• NAIC — Accident and Health Policy Experience Report (2024 data, published 2025), Market Share by Line of Business
• Paul, Weiss — DOJ and FTC issue final 2023 Merger Guidelines (HHI thresholds)