Models predicting the potential spread of the COVID-19 pandemic have become a fixture of American life. Yet each model tells a different story about the devastation to come, making it hard to know which one is “right.” But COVID-19 models aren’t made to be unquestioned oracles. They’re not trying to tell us one precise future, but rather the range of possibilities given the facts on the ground.
One of their more sober tasks is predicting the number of Americans who will die due to COVID-19. FiveThirtyEight — with the help of the Reich Lab at the University of Massachusetts Amherst — has assembled six models published by infectious disease researchers to illustrate possible trajectories of the pandemic’s death toll. In doing so, we hope to make them more accessible, as well as highlight how the assumptions underlying the models can lead to vastly different estimates. Here are the models’ U.S. fatality projections for the coming weeks.
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Forecasts like these are useful because they help us understand the most likely outcomes as well as best- and worst-case possibilities — and they can help policymakers make decisions that can lead us closer to those best-case outcomes.
And looking at multiple models is better than looking at just one because it’s difficult to know which model will match reality the closest. Even when models disagree, understanding why they are different can give us valuable insight.
How do the models differ?
Each model makes different assumptions about properties of the novel coronavirus, such as how infectious it is and the rate at which people die once infected. They also use different types of math behind the scenes to make their projections. And perhaps most importantly, they make different assumptions about the amount of contact we should expect between people in the near future.
Understanding the underlying assumptions that each model is currently using can help us understand why some forecasts are more optimistic or pessimistic than others.
Below are individual forecasts for all 50 states and the District of Columbia.
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