Tokio Marine HCC’s 2026 Annual Stop-Loss Market Report, published June 3, shows January 2025 specific claim trends running 9.2 percentage points above the 2019 to 2023 five-year average. That is nearly double the 5-point overshoot recorded in January 2024, and it means trend factors calibrated to recent historical baselines are already behind the curve for self-insured employers setting attachment points and aggregate corridors.
The acceleration in numbers
Claims above $2 million have surged 213% since policy year 2020. The frequency increase fans out across every major threshold: claims above $200,000 rose 46 percentage points, above $500,000 rose 75 points, above $1 million rose 112 points. The pattern is not limited to the catastrophic tail; it runs through the entire severity distribution, consistent with the doubling of $1 million-plus claimant prevalence documented by the Aegis Risk survey earlier this year.
Cancer now accounts for 35% of total paid stop-loss claims, growing its share for four consecutive years. Cancer and cardiovascular disease combined represent over 48% of total costs, up from 44% in 2021. Record organ transplant volumes in 2025 (49,065 total, including 4,587 heart and 12,344 liver transplants) add another layer of high-severity frequency.
The most striking finding sits in the pediatric data. Children under age 10 represent 39% of all $1 million-plus stop-loss claims, more than triple any other age group. Infants under one year average $1.37 million in severity for claims above $500,000, driven by perinatal complications, congenital conditions, and what the report links to maternal obesity and later-age pregnancies.
Who it affects
Self-insured employers purchasing specific stop-loss, particularly mid-size plans (500 to 5,000 covered lives) where a single neonatal or cancer claim can breach the attachment point and blow through the aggregate corridor. Plan sponsors retaining more risk, a trend Lockton documented earlier this year, face amplified exposure. Stop-loss carriers, brokers, and TPAs pricing renewals into 2027 are also recalibrating; Cigna and Sun Life executives confirmed in early June that stop-loss cost trends continue to worsen faster than expected.
The reserve mechanism: attachment point erosion
When specific claim frequency accelerates faster than the trend factor embedded in the stop-loss pricing model, claims that historically stayed below the attachment point begin breaching it more frequently. The expected claim ratio for the employer’s retained layer needs upward revision. IBNR for the self-funded plan’s retained portion also increases because the development pattern for the retained layer is shifting: more claims now cross the threshold, altering the completion factor at each lag month. If the aggregate corridor was sized using 2019 to 2023 trend assumptions, a 9.2-point overshoot compresses the margin between expected and actual aggregate claims to near zero.
What this means for your next review
Ask your actuary whether the stop-loss trend factor underlying your current attachment point is still based on the 2019 to 2023 average or has been updated to reflect the 2024 to 2025 acceleration. If your plan has set an attachment point below $500,000, the 75-point frequency increase at that threshold means your retained layer is absorbing claims that the prior trend pick assumed would stay below the line. Plans with significant neonatal or oncology exposure should model those claim categories separately; the 39% pediatric concentration above $1 million is not a tail event, it is the central tendency. Request a mid-year claims extract from your TPA and compare year-to-date specific claim penetrations against the assumptions in your last IBNR study.