I do not know how to answer your question. We tried to compare data obtained from the general population. Sometimes studies have been carried out on people in specific occupations, but it is always difficult to determine whether or not these studies are representative. Moreover, whether members of the target group have the same social and demographic profile also needs to be taken into consideration. For instance, if we compare an occupation that has more women than men, we have to adjust the ratios. A true comparison of studies side by side really involves a large number of statistical adjustments. Otherwise, we wind up comparing apples to oranges.
On March 4th, 2008. See this statement in context.