The arc of coronavirus cases in Italy is frightening, continuing to jump by hundreds each day. But a public-health official looking at those numbers will see definite signs that the nationwide lockdown, imposed to keep individuals apart and the virus from spreading, is working. The data look very different when plotted on what is called a logarithmic scale. In a typical graph, values on the (vertical) y-axis are plotted linearly: 1, 2, 3, and so on, or 10, 20, 30, or the like. By contrast, in a logarithmic plot, each tick on the y-axis represents a tenfold increase over the previous one: 1, then 10, then 100, then 1,000, then 10,000 and so on.

Source: New York Times March 20, 2020 19:07 UTC