(2021-12-22) ZviM What's Up With The CDC Nowcast?

Zvi Mowshowitz: What's Up With the CDC Nowcast? The CDC nowcast last week was 2.7% Omicron. That seemed like a reasonable guess.

The CDC nowcast this week is 73% Omicron, and last week’s nowcast got revised from 2.7% to 12.6%. That’s two retroactive extra doublings last week, and then four more in the following seven days relative to Delta, for a doubling time of less than two days.

There are three huge problems with the nowcast’s answer, on top of the revision being rather large and not inspiring confidence.

Where are all the cases?

The regional numbers make even less sense.

Also, it’s averaging over a week so it’s implying even higher rates now.

This is another good explanation of some of the reasons the data doesn’t add up. This is how one should approach the situation when algorithms produce obvious nonsense. As he notes, this isn’t a knock on the CDC. I can be harsh on the CDC, but this isn’t the time and place for that. It is an example of them doing their best to be helpful, and failing to notice that their algorithm had produced nonsense because they didn’t have a human look at it.

And sure, given how many eyes were on the forecast they should have had a human do a sanity check and put in a warning note

Why Does It Matter?

Two reasons. There’s the usual reason to always care, and also the implications of the 73% number would be bizarre and force large modifications in our world model.

The next time the media runs similar headlines, you’ll want to notice their conflation of projection and measurement, and also notice you are confused right away, and react accordingly

If we were already at 73% Omicron last week (with 95%+ in some regions) then as was discussed above, where the hell are the cases?