Stop-Loss Specific Claims Trend Hit 18% in 2025: The Attachment Adequacy Deficit Running Into 2027 Renewals

Specific claims trend for self-funded employer stop-loss ran at 18% in 2025, 9.5 percentage points above the 2019 to 2023 baseline and 4.2 points above 2024's already-elevated 13.8%. Tokio Marine HCC, one of the largest US stop-loss carriers, said it was "undeniably surprised" by the magnitude (BenefitsPro). Attachment points set before the mid-2024 surge are underinsured against the distribution that emerged in 2025.

Key Takeaways

• 18% specific trend in 2025, against a gap to the five-year average that widened from 5 points in January 2024 to 9.2 points a year later. Cigna and Sun Life reported consistent experience, so it is not one carrier's book.
• Claims above $2 million rose 213% from policy year 2020 through 2025, while claims above $1 million now touch 49% of the 1,268 plan sponsors in the Aegis Risk/IFEBP survey against 23% a period earlier.
• Frequency rose 46 percentage points at the $200,000 threshold and 247 points at $2 million. The distribution thickened in the tail rather than shifting uniformly, which is what breaks an excess loss factor table.
• Premium at the $1,000,000 attachment jumped 27.8% in one year, from $13.84 to $17.69 per covered employee per month, against 8.8% at $100,000.
• Children under ten account for 39% of stop-loss spending above $1 million, and infants under one average $1.37 million in severity on cases above $500,000.

What Is Inside the 18%

No single category carries it. Tokio Marine HCC cited frequency increases across all severity thresholds, concentrated in cancer, neonatal and infant care, and transplant, with secondary contributions from Medicare Advantage reimbursement cut-throughs, tariffs on medical supplies and physician supply constraints.

Cancer was named a catastrophic claim driver by 92% of plan sponsors in the Aegis Risk/IFEBP survey, up from 83%, and cancer plus cardiovascular disease accounted for over 48% of total stop-loss claim cost in 2024 against 44% in 2021. The channel is unit cost rather than volume. CAR-T cell therapies carry wholesale acquisition costs of $373,000 to $475,000 per course, with total episode cost including inpatient management routinely above $1 million.

The other end of the age distribution behaves the same way with none of the same controls. Infants under one average $1.37 million in claim severity on cases exceeding $500,000, and children under ten account for 39% of stop-loss spending above $1 million. Premature birth, congenital conditions and neonatal intensive care have no prior authorization lever a stop-loss underwriter can pull at the group level.

That mix is the modelling problem. A trend model calibrated to one category's rate of change underprices the residual, and the survey's own framing puts the scale of the move plainly: "$3 million claims are the new $1 million claim."

The Leverage Is in the Excess Loss Factor

Specific stop-loss pays each dollar above a contractual specific deductible, and its price comes from the excess loss factor: expected losses above the SD as a share of total expected plan cost. The ELF is not linear in the SD. Because the tail carries lower probability mass and higher variability, a given rightward shift in the severity distribution raises the ELF far more at high attachment than at low. That is why 18% specific trend is not simply twice as bad as 9%.

Specific Deductible Threshold	Percentage-Point Change in Claim Frequency
$200,000	+46 percentage points
$500,000	+75 percentage points
$1,000,000	+112 percentage points
$2,000,000	+247 percentage points

The frequency gradient shows what actually happened. Claims above $200,000 rose 46 percentage points; claims above $2 million rose 247 (Insurance Business America). A uniform trend factor applied to an ELF table calibrated on pre-2024 data gets the answer wrong at exactly the attachment points where the money is, because the shape changed, not just the location. An ELF built from a lognormal fitted on 2019 to 2022 experience understates the exceedance probabilities the current oncology and cell-therapy mix produces at $1 million and above.

The attachment gap follows arithmetically. A group that set a $175,000 SD in 2022 on an 8% specific trend assumption was implicitly projecting about $220,000 for 2025. Under 18% trend, the actuarially equivalent figure sits closer to $260,000. Renewing at $260,000 to restore pricing adequacy leaves the employer absorbing every claim between $220,000 and $260,000 that the original pricing would have covered: a $40,000 per-claimant gap, multiplied across each high-cost member.

Carrier premium confirms where the correction is landing. Average monthly specific premium at the $100,000 deductible rose 8.8% in 2025 to $229.40 per covered employee, 10.1% at $500,000, and 27.8% at $1,000,000, from $13.84 to $17.69. The gradient tracks the ELF leverage rather than the headline trend.

The Aggregate Layer Is Moving at the Same Time

Fixing the specific layer does not restore the plan's position, because aggregate stop-loss is recalibrating on the same renewals and partly on different drivers.

Aggregate covers total claims above a corridor over expected, typically 120% to 130% of expected net retained claims, and the attachment in dollars derives from the expected claims projection. When specific trend exceeds the assumption inside that projection, expected claims are set too low and the corridor triggers sooner than priced.

Carriers are widening the corridor factor and raising the base together. A plan that bought aggregate at 125% of a $2.0 million expected claims projection in early 2024 may be offered 130% of a revised $2.3 million figure at renewal, moving the attachment from $2.5 million to $2.99 million. The employer absorbs more retained aggregate risk in the same renewal that raised its specific deductible. Plans that ran close to their corridor in 2023 and 2024 can find the recalibration pushes the attachment past their retained claims entirely, removing recoveries already built into the benefit budget.

GLP-1 medications sit almost entirely in this layer. At $15,000 to $25,000 a year gross, they fall below the specific deductible for most groups, so they raise total plan cost and aggregate exposure without appearing in specific-layer claims. Aggregate expected claims are therefore rising faster than specific expected claims, compressing the corridor buffer at the same moment the specific layer is repricing.

Groups with documented oncology histories, recent large neonatal claims or members on high-cost specialty pharmacy regimens meet both effects at once, and meet them alongside laser provisions and named-individual exclusions that can lift effective coverage cost 30% to 50% above a 2022 to 2023 baseline. The two layers were designed to fail independently. They are not currently doing so.