Thank you for your thoughtful reply.
Regarding the proportion of resolved cases being too small... Hmmm... I’m going to have to think about that.
You’re right that it seems to kill the weak fast and then picks off a steady stream as the cases resolve. The effect that will have on the final numbers won’t be known until, well, when the pandemic is over. That’s the nature of the Case Fatality Rate. However, it’s still worth looking at the CFR while the pandemic is underway. And I do believe that 3,000 closed cases is enough to make it worth looking at that number.
But for the sake of argument, let’s assume that there are 10 times as many closed cases in the U.S. as have been reported, and that all of them fall in the “recovered” column. Then the math becomes, with up-to-the-minute numbers from Worldometers:
1100 / (1100 + 18,630) = 5.6%
That’s a pretty high fatality rate. Higher for sure, than the seasonal flu.
I call it the “instantaneous CFR” for the reasons you described.
It is not a worthless stat, but as you say, we won’t have the final number until this is over.
What I look for is the convergence of the Deaths-to-Cases Ratio (DCR) and the CFR. Once those are close - they will by definition converge once all the cases are resolved - the numbers become more meaningful.
Right now the expected final CFR in SK and on the DP are pretty easy to ballpark. It was trivial to predict that SK’s and DP’s CFRs could only climb when the rates of change of the CFR and DCR were compared. For SK, under 2% CFR might even be optimistic. But unless there is a big tail spike in the case of SK and DP the final numbers will be in between the current DCRs and CFRs.
For most other countries it’s too early to predict. The DCR could decrease and take the CFR with it - I expect that in the US as testing becomes much more prevalent and more mild cases are documented (not discovered, we know how many there are, roughly). But if more local HCSs are overwhelmed, it could go the other way. Too early to be sure.