 Between 1967 and 1969, Marmot examined some 18,000 male civil servants aged between 40 and 69 years old. By placing a flag on their records at the National Health Service (NHS) Central Registry, Marmot was able to track the cause and date of death for each subject who later died. His data are unusually good data. To begin with, they are generated from data-points on specific individuals. Each datum reports the relation between the occupational rank of a particular person and the life-span (and cause of death) of the very same person. By contrast, almost every other study begins from aggregate data. In addition, a number of important background factors are held constant for this study population. Notably, all the subjects in this study are stably employed, they live in the same region (greater London), and all have free access to health care provided by the NHS.