In Belgium, > 0.06% of the population has died from C19. So obviously the mortality rate has to be at least that high. In NYC, the figure is 0.15% (not 0.2%–yet–as the article states). Moreover, if you take the antibody data from NYC at face value, the mortality rate is 0.6%. Same with Long Island and Rockland/Westchester. Some currently positive people would not yet have developed antibodies, which could raise the estimate of infected people, but on the other hand, studies of excess deaths–comparing all deaths this year with an equivalent time period last year–suggest that deaths are undercounted. The study suggested the number of deaths in NYC should be increased by about 16%, while those in L.I. by a whopping 47%. In addition, since about 75% of the confirmed cases in NYC are active, any estimate of mortality rate by deaths/cases underestimates the rate, since many deaths are yet to come from those active cases.