Okay, I'm going to get to the rate in a minute.
One of the first suggestions that comes to my mind: I know that in Vancouver we have police officers permanently located in schools, so there's a police presence in a school. It occurs to me that for a major urban hospital, where we can predict a crime, an assault, being committed every day in that location, would it not make sense to establish a permanent police presence in the emergency ward of a hospital, not security guards, octogenarians or people with radios, but a police officer as a prevention?