 Figure 1  presents the Whitehall data after 25 years of follow-up. It reports age adjusted all-cause mortality rate ratios by employment grade, for three periods of follow-up. A mortality rate ratio reports the proportion of deaths in a given group divided by the proportion of deaths in the reference group. There are four grades in the British Civil Service employment hierarchy: administrative (highest), professional/executive, clerical, and “other” (lowest). The professional/executive grade has been used as the reference group, so its mortality rate ratio is 1.0 by definition.