Between 2013 and 2023, the top 10 hospitals' share of Medicare inpatient payments grew from 4.34% to 6.58%. That's a 52% increase in concentration at the very top of the market, even as total Medicare inpatient spending fell.

Those two facts together tell a story worth examining closely.

The Shrinking Pool, the Growing Share

Total Medicare inpatient payments peaked at $85,092,950,734 in 2019 and fell to $73,336,526,424 by 2023. Over the same decade, the number of hospitals receiving Medicare inpatient payments dropped from 3,294 to 2,941. Fewer hospitals, less total spending, but a larger fraction of that spending flowing to the top.

The top 50 hospitals' share rose from 13.92% in 2013 to 18.10% in 2023. The top 100 went from 22.11% to 27.07%. Put differently, roughly 3% of hospitals now account for more than a quarter of all Medicare inpatient dollars. For a federal program that functions as the single largest purchaser of inpatient care in the country, that degree of concentration has real budget implications regardless of what drives it.

The trend accelerated after 2019. The top 10's share crossed 5% in 2020, 6% in 2022, and kept climbing. The years when total spending fell the most were also the years when concentration grew the fastest.

Volume Explains Some of It, But Not All

High-volume hospitals don't just treat more patients. They collect a disproportionately larger share of payments relative to their discharge volume.

The top 10% of hospitals by discharge volume (349 hospitals) account for 41.13% of discharges but 47.33% of payments. Their average Medicare payment per discharge is $13,892, compared to $9,493 for hospitals in the third-lowest decile. That's a 46% gap in per-discharge payment between the highest-volume and mid-low-volume tiers.

This gap matters because it means concentration compounds. High-volume hospitals don't just treat more patients; they collect more per patient. As volume consolidates into fewer institutions, the payment concentration effect is amplified beyond what discharge numbers alone would predict.

A Decade of Structural Shift

The bottom 10% of hospitals by volume, 350 facilities, accounted for just 0.11% of discharges and 0.10% of total Medicare payments in 2023. These are not rounding errors in the federal budget. But their continued presence in the system, alongside the accelerating dominance of the top tier, illustrates how bifurcated the inpatient market has become.

A decade ago, the top 100 hospitals controlled about $1 in every $4.50 of Medicare inpatient spending. Today they control about $1 in every $3.70. If the trend line from 2019 to 2023 holds, the top 100 could approach 30% of all Medicare inpatient payments before the end of the decade, even if total program spending continues to decline.

The question the data raises but doesn't resolve: the top 10% of hospitals by volume receive payments that are 46% higher per discharge than mid-tier hospitals. Whether that premium reflects genuinely more complex cases, a different procedure mix, or something about how rates are set for dominant institutions is exactly what analysts and auditors should be asking right now.