In the country of Seligia where asbestos has been used extensively in construction, that use is about to be banned, because the exposure of construction workers to asbestos can cause a certain type of cancer. We can predict that the ban will result in reducing the incidence of that type of cancer in Seligia by as much as 50 percent. It is true that less than 30 percent of the death certificates of Seligians who have died of that cancer have "construction" listed as the deceased's occupation. The cancer takes about 20 years after exposure to develop, however, and Seligians who have worked in construction commonly turn to less strenuous occupations as they age. Seligian death certificates indicate only the deceased's last occupation.