Is Covid-19 Growing Exponentially or Polynomially?

The short answer is, I don’t know.

Exponential growth, in the long run, is much worse. Of course, in the long run, exponential growth of any disease (or anything else in the real world such as Ponzi schemes, compound interest) becomes impossible, because whatever-it-is runs out of people (or whatever) to infect.

I am not a real statistician, but I’ve tried plotting the numbers of reported US cases of COVID-19 and of fatalities against the date (starting March 13), and asking Excel and my TI-84 calculator to calculate and graph various “trendlines” (or correlations) using linear, logarithmic, exponential, power, and polynomial models — curves that you might have studied in math class.

Bad news: the graph is DEFINITELY not linear (that is, the points do NOT lie on a straight line, and the number of cases and deaths so far are NOT rising by the same amount each day).

I tried exponential growth, wherein the number of cases/deaths increases at the same RATIO (or percentage) each day. GOOD NEWS: those numbers don’t fit very perfectly. (I’ll show you graphs later.) the plotted points, recently, lie BELOW the exponential curve of best fit. YAY!

What fits best so far is polynomial growth with degree 3 or 4. (Using figures up thru yesterday, I get F=1.256*d^3 – 68.18*d^2 + 1245*d – 7447, where F means the number of Corona virus fatalities in the US and d is the number of days starting from March 1.)

Not that polynomial growth is something we want to continue!

If it did, and the current polynomial-of-best-fit continues to work, then by my calculations, we would have about half a million dead in the US alone by the middle of June.

And not that my model has any fundamental validity — after all, if you plug in d=0, ie February 29, you get that there were NEGATIVE 7,457 fatalities from the new Corona virus which is absurd.

However, the fact that the curve is showing less than strictly exponential growth is good. Now, if we could get EVERYBODY to take physical-social distancing seriously, AND get needed supplies and tests to hospitals and clinics, we could beat it down to zero.

Published in: on April 6, 2020 at 4:42 pm  Leave a Comment  

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