The Field Guide to Understanding Human Error, 2nd Edition

8 You Can’t Count Errors

Many people believe that getting a grip on their “human error problem” means quantifying it. If only they could put a number on it, then they would have a better idea of how much people violate, how often they go wrong, and where. Managers typically like these numbers. In fact, management often occurs by numbers. So why not safety? We all think we know that a stubborn 70 per cent of mishaps is still due to human error. So if you can make the error count go down, your system has becomes safer. Right?

Wrong. As Richard Cook reminds us, it is a mere myth that 70 per cent represents the distance we have to go before we reach full safety. This myth suggests that full safety lies somewhere on, or beyond, the horizon, ...