I see what you're saying. Obviously Medicare rates aren't negotiated, they're set by the government. But physicians don't have to participate. So your point is that doctors only agree to see Medicare patients, and accept lower reimbursements, because they can make up the difference win privately insured patients.

Makes sense. Is it true in actual experience though?

But--we're often told things like 80 percent of lifetime medical expenses happen in the last ten years of an individual's life, when presumably they are (largely) on Medicare. And I think I've read that Medicare comprises something like 40% of all medical payments in the US. And I also know that private insurers are squeezing costs wherever and whenever they can, including tightening allowed payments per service, negotiating network deals etc. So the difference between private insurance reimbursement and Medicare reimbursement is shrinking.

This is a corollary to an earlier discussion about physicians "going concierge" en masse if Medicare-for-all were to be enacted. Is that a viable alternative for the non-exceptional doctor, when every patient is on Medicare? I mean, 80% of doctors aren't in the top 20%, you know? Will concierge practice support more than the top 20%, or maybe the top 40%? I doubt it but I don't know.