A robust critique of Ministry of Health modeling?

It is important and healthy to have people critiquing official Covid modelling, even if they have available much more information than earlier models were based on.  But critiques are open to criticism too.

David Farrar ar Kiwiblog has posted A robust critique and refers to the “key takeaway” from Ian Harrison at Tailrisk Economics critiques the modelling done by the Ministry of Health:

When we ran the Covidsim model we found credible paths that could reduce the pace of infections to sustainable levels. Deaths in the range of 50 – 500 over a year are more realistic numbers. 500 deaths is around average for the seasonal flu. We found that the higher OCRG numbers were mostly generated by their assumption that tracing and testing would be abandoned.

This OCRG assumption is almost incomprehensible, unless there was a deliberate attempt to blow up the numbers. Whether the Ministry was ‘in on it’, or simply didn’t understand what was being reported to them, we do not know. We have attempted to discuss the issue with the OCRG but have had no response.

Farrar comments “So the figure of potentially 14,000 dead was not at all robust.”

Perhaps that was too high, knowing what we know now. But how robust is “Deaths in the range of 50 – 500 over a year are more realistic numbers”?

New Zealand took drastic action and if we play safe in relaxing restrictions we may come out somewhere near the lower end of that range. But what if we had taken a more relaxed approach?

Sweden has about twice our population and has had 1,511 deaths in about a month. That equates to about 750 deaths in a month here, so we could easily have been outside Harrison’s 50-500 range in a year.

Switzerland has a little more population and in a month has had 1,368 deaths. At a similar rate New Zealand would have had about 800 deaths in about a month. If that rate continued for a year we would have close to 10,000 deaths.

New York has had 17,761 deaths so far, and at that rate we would have had several thousand deaths. New York is quite different to here, but it shows how quickly and deadly Covid-19 can be.

Whether we would ever have got to anywhere near 14,000 deaths in a year remains debatable, but we could easily have gone past 500 in a month let alone a year – and we are yet to find out how the virus and the death rate progresses.

The robustness of the MoH models should certainly be examined, but so should the robustness of any critiques.

There isn’t much coverage of Harrison’s criticque, but it gets some support here at Croaking Cassandra: Coronavirus economics and policy: from the mailbox and it comes up in comments at interest.co.nz here.