http://www.salon.com/books/feature/2005/03/17/media/index3.html

Violence has clearly been decreasing in the Western world for the last 500 years; as far as we can tell from uneven record-keeping, the murder rate in medieval Europe was several times higher than it is today, even in relatively violent societies like the U.S. While the 20th century has seen some spikes in violent crime -- correlating less to the arrival of television than to the proportion of young men in the population -- the downward trend since about 1980 has reinforced the general tendency. As Rhodes puts it, "We live in one of the least violent eras in peacetime human history."

http://www.motherjones.com/commentary/columns/2000/06/violent_media.html