I think that single payer is a great plan for a country. I don't think that its cost-saving merits would be evident in a single-state experiment. If California alone offered single-payer health coverage I would expect it to become a magnet for people with expensive health problems from the other 49 states, who either currently pay a lot for medical care or go without medical care. The savings of a single-payer system for Californians could be swamped by the increased costs from people who become Californians out of medical desperation. And then every vested interest currently opposed to American single payer health service would say "see, we told you it's too expensive."
Individual states could easily experiment with e.g. gay marriage or legalizing cannabis before the rest of the country, because the first has negligible revenue impact and the second actually enriches state coffers. But I don't think that you can run the same one-state experiment with single payer health care without incurring steep costs from medically desperate migrants from other states.
As a corroborating fact, there has already been efforts to ship chronically homeless people off to other jurisdictions, since a bus ticket is cheaper to provide than a psych hospital stay. And a good number of the homeless in San Francisco are from elsewhere.
> I would expect it to become a magnet for people with expensive health problems from the other 49 states
OTOH, if the tax-induced cost to business (or even some identifiable subset of businesses) of the single-payer system were less per employee than the cost of provide and manage healthcare benefits, it could also be a magnet for businesses from other states.
This is a good counter argument, although as I see it there are assumptions here that are hard to test.
You started with "I think that single payer is a great plan for a country. I don't think its cost-saving merits would be evident in a single-state experiment." I completely agree that the scale is an important part of how well one could evaluate the success. If you read reference #2 in my comment you saw that Calfornia's GDP is slightly larger than that of France, and France has a universal health care system[1]. My thought is that if it was good enough for an economy like France then California is a large enough test case. I could not make such a case for Wyoming for example.
The argument that 'it would be a magnet, and all these high cost patients would move here' has intuitive appeal but I struggle with it. Here are my challenges with that sort of rebuttal, first I would like to understand better how France deals with the situation given that migration around the EU is fairly easy, and by some accounts France has the best health care, are they over burdened by the high cost cases flooding in? Also there are plenty of reasons to want to live in California but the high cost of living (excluding health care) has been a disincentive for many. As I see it, the set of people who would move to California, for the health care, would be that population who could otherwise afford the cost of living, or by covering their medical costs could now afford the cost of living. And I wonder how big a group that is relative to the overall existing population. I also assume that someone would rather live in a home and pay for health care than be homeless in California and get free health care. There is also the 'reverse' effect where people who are currently bankrupt/underwater and already live in California, becoming productive again after the burden of health care was removed. So what is the net change?
There is also a big fuzzing effect on the healthcare debate which conflates the cost of providing medical services and the cost of insurance. I am convinced by the evidence of concierge doctors and all cash procedures that are significantly less expensive than the 'advertised' or 'billed' prices for procedures, that a form of capture has occurred whereby the medical services providers and the medical insurance providers are colluding (possibly inadvertently) to maximize those costs in order to maximize the transfer of money from patients/businesses into their possession. And while I recognize that state efforts to minimize that (a state insurance commissioner who oversees and regulates that capture) have not been as successful as I would like, I am not convinced that the problem isn't solvable. After all, places like France solved it for some definition of solved.
France has additional factors mitigating against a potential flood of medical-care-seekers:
1) Most (all?) other countries in the EU don't have terrible American-style systems of healthcare provision, so the pull isn't as strong.
2) Language barriers make e.g. a Poland-to-France move more difficult than a Missouri-to-California move, even though the latter move actually requires covering a greater geographic distance.
Of course there are practical barriers against every medically underserved American moving to California to take advantage of a single payer system. My intuition is that there could easily be enough of them to more than cancel the economic benefits that you'd expect from imitating the successful single payer systems of other countries. YMMV. I'd love to be wrong about this.
EDIT: dragonwriter brought up a good point about business-magnet effects, which offsets some of my pessimism about the outcomes of trying this in California. And you have a good point about Californians who might be able to re-enter the workforce.
Individual states could easily experiment with e.g. gay marriage or legalizing cannabis before the rest of the country, because the first has negligible revenue impact and the second actually enriches state coffers. But I don't think that you can run the same one-state experiment with single payer health care without incurring steep costs from medically desperate migrants from other states.