President Trump and his top scientific advisors on the coronavirus taskforce gave a much-anticipated presentation Tuesday night, laying out the data behind the president's recent shift in tone regarding the outbreak – including his decision to extend national social distancing guidelines through May 1.
Specifically, officials pointed to a computer model released weeks earlier by Imperial College London that, at the time, predicted that if no action were taken to slow the spread of the virus, about 2.2 million people in the United States would die over the course of the outbreak.
Then administration officials described separate modeling that predicts that by imposing strict social distancing measures, the toll from the current wave of infections can be reduced to somewhere between 100,000 to 240,000 deaths.
Although officials implied that this estimate was based on the administration's own in-house modeling, they did not provide further details about those calculations. Instead, officials discussed a model from the outside group – the University of Washington's Institute for Health Metrics and Evaluation, or IHME — which produced projections very similar to the administration's findings, according to Dr. Deborah Birx, coordinator of the coronavirus task force.
NPR reached out to two researchers who helped put together IHME's model. We learned of four assumptions made by the model that administration officials did not mention.
Here's what those assumptions are, and why they matter.