Executive Summary: Stop Loss Carriers Are the Actual Architects of Level Funded Plan Design
TOS.06 — The Other Side#
Stop loss carriers do not price risk that others have assembled. They define what is insurable at what cost, and the TPA and employer assemble plan design within that definition. Attachment points, lasers, excluded conditions, aggregate corridor specifications, and contract renewal terms establish the boundaries of what the plan can do. The industry describes this as the employer choosing a plan with stop loss protection. The more accurate description: the stop loss carrier decides what kind of plan is insurable, and the employer chooses within that decision.
Neither attachment point offered to a small employer is a free choice. Both are the carrier’s underwriting decision. The carrier examines census data, age distribution, prior claims experience, industry SIC code, and geographic location, then determines what attachment point it will offer and at what premium. The employer selects from options the carrier designed, at prices the carrier set, subject to terms the carrier wrote. The stop loss market priced $26.9 billion in premium in 2024 according to Allied Market Research, growing at a projected compound annual rate of 15.1 percent through 2034. That market is the underwriting infrastructure whose appetite and terms determine what level funded plans look like at the population level.
The laser makes the architectural role most visible. When a stop loss carrier issues a laser at renewal on a specific member, the employer did not negotiate it and cannot meaningfully appeal it. The member being lasered typically has no idea the adjustment occurred. Their plan document does not change. What changes is the employer’s financial exposure for that member, silently restructured by a carrier decision the member never sees. Tokio Marine HCC’s 2025 Annual Market Report documented that large stop loss claims over $2 million have increased at an average of 26.7 percent per year since 2013.
In 2023, the top three stop loss carriers by direct premiums written were Cigna at $5.0 billion, UnitedHealth Group at $4.4 billion, and Sun Life Financial at $2.7 billion, together representing roughly 45 percent of total stop loss premium. In January 2025, Nationwide announced an agreement to acquire Allstate’s employer stop-loss segment for $1.25 billion, further concentrating the market. When a carrier acquires a book from a competitor, it underwrites absorbed clients at renewal using its own criteria. The employer made no decision that caused this change. Carrier consolidation delivered it.
Behind the carriers sit reinsurers including Swiss Re, Munich Re, Gen Re, and Employers Re, whose appetite determines how much risk the stop loss market can absorb in aggregate. When reinsurers tighten terms, stop loss carriers tighten terms, attachment points rise, and employer plan design options narrow. Voya’s stock fell 11.1 percent and Cigna fell 11 percent in a single week in December 2024 after each announced stop loss results. The financial markets understood that carrier-level results would transmit directly to employer-level plan costs at renewal. If the carrier is the plan architect, the employer’s oversight obligation extends to carrier behavior, not just TPA administration: the carrier’s laser practices, renewal behavior, and aggregate corridor requirements will determine what the plan can do for the next policy year and in which direction it will be adjusted at the following renewal.