UPDATED: A Big Drop-Off in Games with Models, 5/18/20 Data


As my daily COVID-19 hospitalization chart for Rhode Island shows, today’s data brought a major drop-off of about 10% from the day before.

Even better, hospitalizations obviously lag infections, and the data itself is two days behind, and new cases overall are down, too.  Yesterday, only 121 new cases emerged, even though the number of total tests was within the range that we’ve been seeing.  That’s the smallest increase in cases since April 4.  This is despite the fact that we’re now well into the incubation period for anybody who might have caught the virus when things began opening up a bit more.

A question therefore emerges:  What “facts and science” led the governor to decelerate her reopening plans?

Interestingly, one metric she’s said she’s following is the R-naught value, which is a measure of how many people each infected person spreads the disease to.  A value of one means the disease is not increasing; less than one means it’s receding. The governor stated that the value is right now “1 or just under 1.”  However, if the average infection period is 14 days, the numbers of positive cases suggests an R0 of 0.32.

UPDATE: The website rt.live uses a sophisticated formula to estimate when people’s infections began and to adjust for the number of tests conducted each day.  This obviously gets back to the problem I posed at the beginning of this exercise, that every new assumption could actually move an estimate farther from the truth.  For example, correcting for a reduction of all testing and thereby devaluing a drop in positive tests could ignore the fact that people aren’t being tested because they aren’t sick.  In any event, the website puts the R value at 0.85 for Rhode Island, which is in the top half for the country.

News reports give no explanation for the governor’s change of plans beyond stating:

“You don’t know the impact [of changes] until you have observed them for a couple of weeks,” Raimondo told reporters in explaining the current timeline: two weeks for any new cjanges to take hold and then another two weeks to study them.

It doesn’t take much skepticism to wonder whether the governor had expected the improvement of the numbers to go more slowly, naturally spacing out the phases.  But this head fake on the schedule damaged her ability to keep imposing rules, and if things continue to get better, more people will wonder how she has the authority to set regulations more than 30 days out when she has no idea what’s coming.

After all, her statements about continuing economic restrictions are coming at a huge cost to Rhode Islanders.  “Better safe” for her could be “sorry” for thousands of others.


(See here for my original methodology and here for a subsequent modification I made.)

Projections versus actuals (date of report).

  • Cases:
    • Projection for 5/18: 12,799
    • Actual for 5/18: 12,795
    • Projection for 5/19: 12,919
  • Hospitalizations:
    • Projection for 5/18: 258
    • Actual for 5/18: 236
    • Projected for 5/19: 224
  • Deaths:
    • Projection for 5/18: 504
    • Actual for 5/18: 506
    • Projection for 5/19: 511