In three analyses of lethality trends, over time, by type of weapon and across counties, we have garnered considerable support for the hypothesis that advances in emergency medical care have greatly and increasingly reduced the lethality of violent assaults, with observed annual drops in such lethality ranging from 2.5% to 4.5%.Over the 40 years they studied, the total reduction in homicide from better technology was roughly a factor of 4; see figure 1. Thus, there is strong evidence that the homicide rate is not a sign of a more peaceful society, but rather a richer one.
Technology reduces the homocide rate
There's no question that modern technology saves lives. Getting a victim to a hospital as fast as possible is vital. People are helicoptered to trauma centers. It seems like these sorts of technological advances must be affecting the murder rate; but how much? The homicide rate has been pretty flat for a long time, even as other sorts of crime have exploded since the 60s. Here's a paper, Murder and Medicine: The Lethality of Criminal Assault 1960-1999, which characterizes the effect: