We have changed how we are reporting testing and case rates on the Data by State page. Previously, we used the 2018 year end prison population numbers released April 30, 2020 from the Bureau of Justice Statistics for the denominator. Since these data are old, and there have been recent changes to prison populations, we are now using more recent population data collected by the Vera Institute of Justice. For all states, minus the exceptions below, the population data are for April 30/May 1, 2020. For the following states we use population data for March 31, 2020: Montana, South Dakota, Tennessee, and Washington. For the following states we use population data for December 31, 2019: Illinois, Maryland, Minnesota, Montana, New Mexico, and Virginia. These represent the most recent data available.
Our testing rates represent the number of tests per population. It is possible that some states are testing the same person more than once. Only one state is reporting the number of people tested separately from the number of tests given. As an example, Michigan has now reported more tests for COVID-19 (37,885) than there are people currently incarcerated in their prisons (36,980), likely due to releasing people from prison, widespread testing practices (including repeat testing), and deaths.
Last updated June 4, 2020.