Lies, damned lies, and COVID statistics

20 July 2020

As the number of confirmed cases of Covid-19 in the U.S. has skyrocketed, the nation’s case-fatality rate has indeed gone down, to just 3.8 percent, but that number is still higher than in dozens of other countries. It is also essentially meaningless, since nations are testing at different rates and researchers warn that the case-fatality rate is unknowable until after a pandemic ends, when the full death toll is known. In the meantime, it is a misleading way of measuring the lethality of a disease unless an entire population has been tested for it. (Robert Mackey, The Intercept)

The “top of the fold” headline in today’s La Jornada was “Trump: vean a México, en lugar de EU sobre el coronavirus” (Trump: look at Mexico instead of the US on the coronavirus). He apparently has reverted to his old campaign theme of “dirty Mexicans, bringing their diseases, etc.” when.. for all its ills and missteps, the story is that it’s much more probable that the pandemic reached Mexico via the United States, and that Mexico’s infection and mortality rate… alarming as they are… is lower than that in the United States.

An interviewer for the US network, Fox News, was incredulous about the President’s claims that the US was less affected by the virus than most of the world, causing Trump to call for a chart meant to “prove” what he was saying was somehow within the bounds of reason. What he showed was the “observed case-fatality” rate, which (I use the Johns Hopkins database) shows Mexico only behind Great Britain in fatalities per 1000 IDENTIFIED Covid patients, not the fatality rate in the population as a whole. As of this morning, the fatality rate per 100,000 in the US is 42.22 per 100,000, whereas it is 31.05 in Mexico.

The differences in the “observed case-fatality rate” have a lot to do with testing processes. Mexico has been criticized for its limited testing… only a percentage of those already showing symptoms… and only meant to provide public health officials with an estimate of the necessary facilities that would be needed. Whether it has been the best practice, or even effective in its modest purpose, is debatable, although Mexico has not seen the complete breakdown in its public health system we’ve seen in other parts of Latin America, nor is there (overall) any major shortage of intensive care units. On the other hand, it does mean that the likelihood of persons being treated are those who are already very ill, and have a higher likelihood of dying.

But, if you look at overall mortality rates, Only Chile and the United Kingdom are losing more of their people than the United States. The mortality rate per 100,000 in the US is 42.25 while in Mexico it is 31.05.

To echo Tolsti, every pandemic stricken country is stricken in its own way, and comparing the two countries is probably not all that instructive. I don’t know of any statistics comparing mortality among persons with the same economic and social levels (although, everywhere, it’s the poor who die the most): if it is the poor who are most likely to die, one would expect Mexico’s rate to be much higher than the US (at least, if we believe poverty in the US is not as endemic as we’re told).

The media, here and there, has been full of stories lamenting the inability of the Mexicans to “shelter in place” for financial reasons. But, if that is true, why is Mexico’s mortality rate still lower than the US? Age? Mexico has a younger population, but one with more risk factors, like diabetes and obesity? Masks? 85% of Mexicans are wearing masks in public, compared to 67% of people in the US… or so it’s claimed.

This isn’t to say the Mexican “butcher’s bill” won’t rise to the appalling figures seen north of the border, but only that when it comes to statistics and basic science, politicians are not the best source of information.