Incidence

"The fact that the general incidence of leukemia has doubled in the last two decades may be due, partly, to the increasing use of x-rays for numerous purposes. The incidence of leukemia in doctors, who are likely to be so exposed, is twice that of the general public. In radiologists … the incidence is ten times greater."
--Isaac Asimov (1965),
as quoted in Isaac Asimov’s Book of Science and Nature Quotations (1988), 233.