In 2008 "fewer officers were killed by gunfire (41) than in any year since 1956. That compares to 68 firearms-related deaths in 2007." In 1956 "there were 35" while there was a "peak of 156 officers killed by gunfire in 1973."
There are, of course, far more law enforcement officers in the United States now than there were in 1956, so per 100,000 law enforcement officers, this year's gunfire death rate for law enforcement officers is even more exceptional. The years 1953-1955 were all higher in raw numbers of law enforcement deaths from gunfire than 2008 as well. There are currently roughly 700,000 law enforcement officers in the United States (extrapolating to include non-reporting jurisdictions). In 1956, the number was closer to 273,000 police at the state and local level, in addition to some federal law enforcement officers.
So far, 140 law enforcement officers have died in the course of duty in 2008, compared to 181 in 2007. Per 100,000 law enforcement officers, this is near a record low as well.
Traffic accidents are now the leading cause of on the job death for law enforcement officers, for the 11th year running.
Fairly low homicide rates, improved medical care, and increased use of bullet proof vests, and safer police cars have probably all contributed to the low levels of officer deaths in 2008.
The data are from the National Law Enforcement Officers Memorial Fund and another group, Concerns of Police Survivors.