Neither do we know why some people are asymptomatic, why others have mild cases, why still others describe it as the worst illness they’ve ever experienced, why a few end up in the ICU, on ventilators, and die, why some develop much worse, longer-term medical problems in many different organs and systems of the body, and why some people continue to test positive for the virus long after their symptoms have faded. We don’t even know what percentage of the population will need to be infected before herd immunity sets in, halting the spread of the virus without a vaccine.

The list of uncertainties is excruciatingly long. Those who build the models make informed guesses about the answers and then combine those hunches into predictions. We shouldn’t be surprised when reality fails to conform to them.

Which would be fine if the models were constructed as an academic exercise by researchers trying to understand and make predictions about the contours of everyday life. Instead, they’re being used as a baseline for emergency decisions that could have staggeringly high costs — with the possibility of hundreds of thousands or even millions of deaths pitted again economic devastation that plunges the entire world into the worst economic downturn in nearly a century.