What is the significance of the 218%? My understanding is that in non-medicare expansion states, subsidies start at 100% fpl (below that and you have to get on

What is the significance of the 218%? My understanding is that in non-medicare expansion states, subsidies start at 100% fpl (below that and you have to get on Medicaid) all the way up to 400% of fpl reducing to nothing but the time you hit 400%. In Medicare expansion states, subsidies start at 134% of fpl.