The sluggish rollout of the tests has become a debilitating weakness in America’s response to the spread of the coronavirus. By this point in its outbreak, South Korea had tested more than 100,000 people for the disease, and it was testing roughly 15,000 people every day. The United Kingdom, where three people have died of COVID-19, has already tested more than 24,900 people.

The Atlantic reached its new estimate through an ongoing collaboration with the data scientist Jeffrey Hammerbacher and a team of volunteers recruited for their experience with data collection, and after consulting data published by all 50 states and the District of Columbia. States vary widely in their reporting standards. All provide positive case reports. But many do not provide negative or pending case reports, which provide crucial context for both the progression of the virus and the government response to it.

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Our effort is necessary because the Centers for Disease Control and Prevention is not regularly providing data on the full scope of American testing. On its website, the federal agency now provides a number (1,707 as of Sunday) that reflects only the number of people tested at the CDC’s laboratory, even though state and private laboratories provide the bulk of testing. (The CDC did not immediately respond to a request for comment.)

When the CDC has provided data, it has been slow and incomplete.

On Saturday, Stephen Hahn, the commissioner of the Food and Drug Administration, told reporters that 5,861 specimens—not people—had been tested for the coronavirus by the end of the week. As a rule of thumb, it takes about two specimens to deliver results for a single patient, which would make this equivalent to about 2,900 people tested through Saturday.

Last week, The Atlantic reported that it could only verify that 1,895 people had been tested for the coronavirus as of Friday morning.

Testing capacity still varies enormously across the country. Many states, including some of the country’s most populous, are not reporting how many tests they have conducted overall. Texas, which now has 24 positive cases, has not posted on its website how many people it has tested overall. A spokesman for the state said it had tested 150 people as of last week, but “with private labs coming online now, I don’t think we’re going to have a definitive number for the entire state going forward.” Nevada has not reported any new data at all on its health-department website since March 3.

Massachusetts, which has 41 presumptive cases, has not released its total number of people tested. Neither has Pennsylvania, which has 10 presumptive cases. Last week, a Pennsylvania official told us that the state could test only a dozen or so people a day, suggesting that it has a high rate of positives.