How I read the numbers

I saw a FB friend ask why Missouri has 3x more C-19 cases than Kansas and insinuate the difference is in how seriously the Governors of each state is handling it (Kansas more authoritarian, Missouri leaving it up to locals).

Here are some things to think about:

According to Politico’s Covid Tracker, here are the stats as of 3/29, plus the population of each state:

  • KS: 4,513 tests given, 319 positive, 1.8 million state population
  • MO: 12,385 tests given, 838 positive, 6.1 million state population

This means:

  • Missouri has given about 3x the number of tests as Kansas (2.74 to be exact).
  • It has about 3x as many cases (2.63 to be exact).
  • It also has about 3x the population as KS (3.4 to be exact).

So, all the numbers are in close proportion to the states’ populations. It’s not clear that the way the two governor’s have approached the situation have had much of an impact.

Also, both states are running about 6-7% positive rate on tests given. More on that in a later.

As I’ve said in other posts, until there is no bottleneck or selection bias in getting tested, the number of positive cases will be more of a function of the number of tests given and not a good indicator of the actual number of C-19 cases.

The actual number of C-19 cases, I suspect, is higher. Maybe 3 – 10x higher than cases identified through testing.

I know people in both states that have had C-19 symptoms who were not tested because they were not in a high risk group. They were told to go home and self-quarantine, and their conditions improved. They won’t know until they get an antibody test if they had C-19 or not.

But, what is interesting to me is the % positive tests. At 6-7% it could mean a few things:

  • That has come down from 10-15% range in both states just a few days ago. I’ve found with this data, though, that active cases and/or tests sometimes lag each other by a day. Tests given may have been updated and active cases won’t be until tomorrow. So, the 6-7% may not be accurate.
  • If the numbers are accurate and percent positives have truly declined, that tells me that the testing bottlenecks and selection bias are likely decreasing and more folks are getting tested. If so, the 6-7% may be closer to the percent of the population that has had C-19 since the tests started.
    • I don’t know if that’s good or bad.
    • It could be bad if this actually represents the first wave. That means we still have more than 90% of the population to go through.
    • It might be good if these actually represent the 2nd wave (which I still think it might), which might mean that 15-20% of the population has had it and we have less to go.
    •  I still don’t have a good feel for what percent of the population could get it. So, my inherent assumption in the previous two bullets that the virus will work through 100% of the population may be high.


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