Readers commit the same fallacy when they read that “the top one percent in 2008” had incomes that were 50 percent higher than “the top one percent in 1988” and conclude that a bunch of rich people got half again richer. People move in and out of income brackets, shuffling the order, so we’re not necessarily talking about the same individuals. The same is true for “the bottom fifth” and every other statistical bin.

Steven Pinker, Enlightenment now: the case for reason, science, humanism, and progress, New York, 2018, p. 112