Is there a country where market based health insurance works? Specifically where it works without there also being a strong public health insurance option. For

Is there a country where market based health insurance works? Specifically where it works without there also being a strong public health insurance option. For instance in Germany you are required to be insured and as a young healthy person you can save money by choosing a private option. But eventually as you get older your insurance costs will go up. So most people choose and are extremely happy with the public option TK. A private health insurance marketplace seems like the type of industry ripe to take advantage of consumers. And what if the health insurers in the market conspire to fix prices? The government or a class action suit could fight against it but that's the type of corrupt business practice at large that could take over a decade to correct.