pulling from the recent page-long thrashing about a Local (turkey-day-crit) crash
MABRA annually reports "incidents" per event / race / category. On average in the mid Atlantic there is 1 crash per 3 cat 5 races, and 1 crash per 3 cat 4 races. I can't find the reports off hand but a google of mabra.org should yield the results. Incidents are not graded by severity. However there are people who have died during amateur bike racing.
Thoughts on the Dangers of Racing?
Mitigating strategies (how do you know when you can ride safely in a cat X pack)?