The model of coronaplague with the best graphics says that Massachusetts, home to 2% of Americans, will suffer 12% of total COVID-19 deaths (8,219 out of 68,841, through August 4, 2020).
How sure can we be of this result?
“Learning as We Go: An Examination of the Statistical Accuracy of COVID19 Daily Death Count Predictions” (Marchant, et al., April 8, 2020) says “not very”:
Our results suggest that the IHME model substantially underestimates the uncertainty associated with COVID19 death count predictions. We would expect to see approximately 5% of the observed number of deaths to fall outside the 95% prediction intervals. In reality, we found that the observed percentage of death counts that lie outside the 95% PI to be in the range 49% – 73%, which is more than an order of magnitude above the expected percentage. Moreover, we would expect to see 2.5% of the observed death counts fall above and below the PI. In practice, the observed percentages were asymmetric, with the direction of the bias fluctuating across days.
So… the model was “wrong” (actual fell outside predicted 95 percent range) as much as 73 percent of the time!