You’ve heard it over and over: Wearing masks can save lives. Now, leading scientific modelers are putting a number to it—predicting that if 95 percent of Americans were to wear masks outside the home, 66,000 lives would be spared from the coronavirus. The Institute for Health Metrics and Evaluation at the University of Washington’s School of Medicine estimates that if the nation continues on in the current vein, with many people foregoing masks, the death toll by Dec. 1 could nearly double and hit almost 300,000. “We’re seeing a rollercoaster in the United States,” center director Dr. Christopher Murray said in a statement. “It appears that people are wearing masks and socially distancing more frequently as infections increase, then after a while as infections drop, people let their guard down and stop taking these measures to protect themselves and others—which, of course, leads to more infections. And the potentially deadly cycle starts over again.”