OP here. I’m a retired engineer researching US healthcare pricing mechanics.

I analyzed the 10-K filings for the 'Big 3' insurers (United, CVS/Aetna, Cigna) to test the common claim that their profit margins are razor-thin (~3%) and therefore they aren't driving inflation.

The data shows a massive decoupling event in 2018. While margins remained flat (likely due to MLR regulations), total revenue quadrupled following the vertical integration of PBMs. Effectively, they shifted from a 'rate game' to a 'volume game.'

The chart in the post visualizes this split. I also discuss the 'Three-Legged Stool' solution (Residency Caps + MLR + AHPs) to address the structural incentives.