Corrections

October 2020, page 40—In the caption for figure 1, the increase in the number of physics PhDs at US universities over the past 15 years should be 75%.

November 2020, page 28—Daniel Bernoulli, not David, devised a model to predict the benefits of smallpox inoculations. In box 1, the negative binomial distribution should be $P(x;R0,k)=[Γ(k+x)/Γ(k+1)Γ(x)]pk(1−p)x$⁠.