Malcolm Gladwell:

In the early nineteen-seventies, Denny Gioia worked in the recall office of the Ford Motor Company. His job was to read field reports from the engineers Ford had posted around the country. If a safety problem was spotted, the Ford representative in that district would write up the case on a standardized form—single sheet, two sides, sometimes with a photograph stapled to the page—and send it on to Detroit.
 Gioia looked for patterns. “You have to be able to identify something that’s breaking,” he said not long ago. “Otherwise, I’ve got an imaginary event. I try not to engage in magical thinking. I’ve also got to have a pattern of failures. Idiosyncrasies won’t do. Question is, do you have enough here indicating that these failures are not just one-off events?” He was looking for what he called “traceable cause.”