Interesting thought experiment: if NY daily deaths over the next two weeks average 400, that's 5,600 upcoming deaths from people presumably infected now. If about one-third of deaths are not accounted for (5,121 unidentified as a portion of identified+unidentified), then we'd have about 8,400 new deaths projected over two weeks including the likely unidentified deaths.

As a percentage of those who were infected as of this study, that's a 1.3% infection fatality rate.

Obviously some conjecture and estimates there, but it seems to be on the high range of early estimates (though much lower than the 3%+ rates derived from CFR with undercounted denominator).

You can derive that from better data. From https://covidtracking.com/ we can see that 57k people have been hospitalized in New York State so far, with 15k still in the hospital. Of the 42k who aren't, 16k died[1], so we'd expect that about 5k of the people currently in the hospital won't be coming home (some of these statistics are pretty depressing).

So two methods give us similar counts, matching up very closely with the separately measured CFR from way back in the original outbreak. That's pretty good back-of-the-envelope work.

[1] this isn't quite right as not every fatality was a hospitalized case.

The time to go positive on an antibody test is not zero either, probably 7 to 14 days. Also the infection rate is lower now than it was in the past. I doubt this adds up to more than 50% higher mortality.

You are correct, edited.