If the total cost is X% of GDP, then the tax needs to hit that number irrespective of what anyone may have paid before that point.
The Nordics all run around 10% of GDP with better health care, while the US is about 17%. I can definitely see a big portion of that difference coming from Medicare efficiencies, but I suspect there is also a large component of unnecessary care in there as well (both fraud and CYA). We will need to incentivize preventative care as well. Doing so isn't simply "here it is, now you can go see the doctor before it becomes a problem." There's also a large education component and changing behavior will take some time.
The Nordics all run around 10% of GDP with better health care, while the US is about 17%. I can definitely see a big portion of that difference coming from Medicare efficiencies, but I suspect there is also a large component of unnecessary care in there as well (both fraud and CYA). We will need to incentivize preventative care as well. Doing so isn't simply "here it is, now you can go see the doctor before it becomes a problem." There's also a large education component and changing behavior will take some time.