The results show that states with few Covid-19 cases and deaths so far will need to perform relatively few tests: between 68 and 145 per day in Alaska and between 31 and 156 in Montana, for instance. States harder hit by the pandemic face a much heavier lift: New York would have to do 130,000 to 155,000 tests every day, New Jersey 75,000 to 90,000, and both Massachusetts and Illinois about 30,000 to 35,000.

Many hard-hit states are not even close to their goals. New York, for instance, has been averaging barely more than 20,000 tests per day since mid-April. New Jersey has been doing about 7,000, on average. Neither has announced reopening plans or dates, giving them time to ramp up testing. Massachusetts and Illinois are in no better shape, conducting just under 7,000 a day. Michigan, Connecticut, and Colorado are all about 15,000 tests a day below their May 1 targets. Texas, with more than 9,000 tests a day, and Washington state, with more than 3,000, are already doing enough.

The more worrisome gap involves states that, despite having thousands of Covid-19 cases, are easing mitigation strategies by, for instance, allowing more businesses and public spaces such as beaches to reopen. To catch hot spots before they turn into wildfires of disease, Georgia must do 9,600 to 10,000 tests per day; it has been averaging around 4,000. Florida will need 16,000; in the last week it has been hitting just above 10,000. South Carolina is a rare bright spot: It will need 1,200 to 1,600 tests per day and has been averaging close to the low end of that, with at least 1,500 tests on several recent days.