Barbara Wertheim Tuchman defined Tuchman’s Law in A Distant Mirror: The Calamitous 14th Century:
Disaster is rarely as pervasive as it seems from recorded accounts. The fact of being on the record makes it appear continuous and ubiquitous whereas it is more likely to have been sporadic both in time and place. Besides, persistence of the normal is usually greater than the effect of the disturbance, as we know from our own times.
After absorbing the news of today, one expects to face a world consisting entirely of strikes, crimes, power failures, broken water mains, stalled trains, school shutdowns, muggers, drug addicts, neo-Nazis, and rapists. The fact is that one can come home in the evening — on a lucky day — without having encountered more than one or two of these phenomena.
This has led me to formulate Tuchman’s Law, as follows: “The fact of being reported multiplies the apparent extent of any deplorable development by five- to tenfold” (or any figure the reader would care to supply).