The Closed Block Isn't Closed to Change
What the Data Says About Medicare Supplement's Most Overlooked Segment
When most people in the Medicare Supplement industry talk about market strategy, the conversation gravitates toward new business — open block pricing, competitive positioning, and sales velocity. That's understandable. But there's a $11.3 billion segment of this market that too often gets managed reactively rather than strategically: the closed block.
New NAIC data shows that closed block Medicare Supplement business represents $11.3 billion in earned premiums and 3.7 million covered lives across the country. It's nearly 28% of the entire Medicare Supplement market by premium volume — and it's operating under mounting financial pressure that demands better data and faster answers than most carriers currently have access to.
The Numbers Don't Lie: Closed Blocks Are Under Financial Stress
According to the most recent NAIC financial data, the aggregate loss ratio for closed block Medicare Supplement business sits at 86.8% — 1.7 percentage points higher than the open block's 85.1%, and well above the 85.5% market-wide average. In practice, across $11.3 billion in premium, it represents hundreds of millions of dollars in claims pressure above what open block books are experiencing.
Rate Filings Are Accelerating, and the Increases Are Significant
CSG Actuarial’ s Closed Block Rate Change Report — tracking filings across more than 130 carriers — tells a clear story about where the market is headed. In 2025 and 2026 alone, carriers submitted 2,736 rate change filings for closed block Medicare Supplement plans.
Highlights from those filings:
The average rate increase across all recent filings is 11.0%, with a median of 10.5%
More than half of all 2025–2026 filings (53.6%) reflect increases of 10% or more
Over one-third (35.5%) filed increases of 15% or higher
Nearly 15% of filings reflect increases of 20% or more
Plan-specific pressure is even more pronounced. Plan F — historically the most popular Medicare Supplement plan before the 2020 changes and still the dominant plan in most closed blocks — is averaging an 11.8% rate increase in recent filings. Plan G, increasingly common in closed blocks as the pre-2020 era book matures, is seeing even steeper pressure at a 12.9% average increase.
Geographically, the filing activity is concentrated in the largest markets: Texas, Pennsylvania, North Carolina, Tennessee, and Ohio lead the country in closed block rate filing volume for 2025–2026, a reflection of both market size and the aging demographics in those states.
Why this matters for everyone in the Medicare Supplement ecosystem? How carriers manage these aging books — and how effectively they use data to do it — will shape their financial results for years to come. $11.3 billion in premium, 3.7 million lives. An average rate increase of 11% filed across the board in 2025 and 2026 alone. The closed block is one of the most financially consequential segments in the Medicare Supplement market — and it's becoming more complex every year.