Executive Summary: The Stop Loss Market: Carrier Concentration, Loss Ratios, and Capacity Cycles
LFP-02.06 — The Risk Layer#
The U.S. employer stop loss market generated approximately $35.5 billion in annual premium in 2023, covering 61 million people through self-funded plans, and grew at a compound annual rate of 11.9% from 2018 to 2023. Approximately 10% of growth reflected cost trends and business mix changes; the remainder came from enrollment migration out of fully insured arrangements, which declined 14.2% over the same period according to Oliver Wyman.
The market divides between independent carriers and carrier-affiliated products. Independent carriers sell stop loss into the TPA distribution channel, where employers select a TPA for administration and a separate carrier for risk. Sun Life is the largest independent carrier by NAIC premium data. Voya Financial covers approximately 2.2 million employees. Symetra, HM Insurance Group (a Highmark subsidiary), Berkley Accident and Health, Tokio Marine HCC, and QBE North America are additional major participants. Nationwide’s $1.25 billion acquisition of Allstate’s employer stop loss segment, completed July 2025, created a significant new entrant serving over 13,000 small businesses. Prudential Financial launched a new stop loss product in September 2024. Carrier-affiliated products bundled within proprietary level funded offerings from UnitedHealthcare, Cigna, and Aetna control a substantial share of the small group market through the simplicity of a single-contract arrangement.
Loss ratios deteriorated from 79.5% in 2018 to 80.3% in 2023. The Guy Carpenter report documented a steeper deterioration from 78.5% in 2017 to 84.1% in 2022. Claims exceeding $1 million increased more than 34% over a recent three-year period; claims exceeding $2 million rose 62%; claims exceeding $5 million rose 275%. Cancer treatments, premature births, and specialty pharmacy costs drove large claim growth. Voya’s Q3 2024 benefit-to-premium ratio reached 93.4%, up from 83.3% a year earlier; operating gain fell from $51 million to $29 million; new stop loss sales fell from $67 million to $35 million as the carrier tightened underwriting. Among 1,268 plan sponsors surveyed in the 2025 Aegis Risk report, 49% now report claims in excess of $1 million, up from 23% in 2024. Single-year premium increases of 8.8% to 10.5% followed.
When carrier loss ratios are elevated, employers receive renewal increases regardless of their own group’s claims experience. A 20-person group with clean claims in a year when the carrier’s aggregate book performed poorly still receives a renewal reflecting portfolio-level repricing. Small groups are disproportionately affected during hard markets: the risk-reward ratio for small group stop loss is the least favorable in the carrier’s portfolio, and when capacity restricts, small groups are the first segment carriers exit. An experienced stop loss broker who can distinguish whether a renewal increase reflects group-specific repricing, book-wide repricing, or carrier appetite restriction provides information the employer cannot obtain independently, and that distinction determines whether the employer should accept the renewal, negotiate, shop alternative carriers, or evaluate returning to fully insured.