Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.) are catching lots of flak for the cost of their “Medicare for All” (MFA) proposals and the feasibility of raising the requisite extra revenue. There are lots of numbers floating around, but our central cost focus should be on national health expenditures as a share of GDP. This is particularly important in thinking about MFA, because private-sector health care spending would be replaced by public-sector health care spending.