In the March 18th post you can find here, I projected the number of COVID-19 cases in the USA at the end of April under four scenarios: “Like South Korea”, “Like China”, “Like Italy” and “USA “Business as Usual””. Due to the nature of exponential growth rates, the resulting number of cases in the USA at the end of April ranged from 10,000 to 10,000,000. The key difference between these scenarios is the day-over-day reduction in case growth rate. It varied from a 14% day-over-day reduction for South Korea to a 1.4% day-over-day reduction for the USA.
I have been monitoring the state-level numbers over the last five days. Unfortunately, the USA continues on the “Business as Usual” trajectory. The figure tells the tale. It is a plot of all the state’s day-over-day change in case growth rate versus that state’s proportion of the USA population. The four largest states average a day-over-day rate reduction of 1.2%. All of the rest of the states pull the overall average reduction closer to 2%.
Change in State Day-Over_Day Case Growth Rate versus State’s Proportion of USA Population
The day-over-day reduction needs to be larger than 5% to match even Italy. The larger states have taken a mixed array of actions over the last few days which may help over the next week. We’ll see.