With hindsight, it is easy to point the finger of blame at smoking. If we plot the rates of lung cancer and tobacco consumption on a graph (see Figure 5.2), the connection is impossible to miss. But time series data are poor evidence for causality. Many other things had changed between 1900 and 1950 and were equally plausible culprits: the paving of roads, the inhalation of leaded gasoline fumes, and air pollution in general.
