COVID-19 models vary widely. What that means for leaders under pressure.

Determining a rational course of action can be challenging when fear abounds. Understanding the underlying assumptions that have led to dramatically different projections of COVID-19 infection and fatality rates can help.

As mayors, governors, and presidents weigh how best to guide their communities through the coronavirus crisis, they must navigate dramatically divergent models of the arc of the pandemic.

In the United States alone, leaders have already made decisions that have disrupted millions of citizens’ lives and cost trillions of dollars, with a disproportionate economic impact on low-wage earners and...