Would I have to pay more?

A single-payer plan does not mean free health care. Consumers would shoulder some cost, but how much is unclear. Taxes would probably replace premiums, deductibles, co-pays and other out-of-pocket expenses. But the overall cost of single-payer health care depends on the system design. In some countries with public systems, patients pay out of pocket for dental and vision care. Some also buy supplemental insurance.

Most single-payer advocates say out-of-pocket costs could drop because the taxes consumers would pay to foot the overall bill would be based on income rather than on an insurance plan. Critics aren’t so confident, because tax rates for the program could increase over time. Californians spent about $7,549 per capita on health care in 2014, according to the federal Centers for Medicare and Medicaid.

The big unknown, opponents of single-payer plans note, is how steeply—and how often—taxes would rise. They also worry that other costs could be added over time.