Stephen Pinker has noted the same phenomenon and argues:
Violence has been in decline over long stretches of history, and today we are probably living in the most peaceful moment of our species' time on earth.This long term trend has several important implications.
The decline of violence is a fractal phenomenon, visible at the scale of millennia, centuries, decades, and years. It applies over several orders of magnitude of violence, from genocide to war to rioting to homicide to the treatment of children and animals. And it appears to be a worldwide trend, though not a homogeneous one. The leading edge has been in Western societies, especially England and Holland, and there seems to have been a tipping point at the onset of the Age of Reason in the early seventeenth century.
First, the seemingly endless dispute between Hobbes and Rosseau has been finally settled. Hobbes famously argued that the natural state of mankind is "nasty, brutal, and short." Rosseau, on the other hand, posited the existence of a "noble savage" uncorrupted by civilization. It seems that Hobbes had it right -- the progress of civilization has been accompanied by a decline in the incidence of violence.
Second, theories intended to explain short-term declines in violence are inadequate to explain the long-term trend emerging from several independent studies. Pinker notes three alternative explanations that have recently been offered.
1) Increasing peacefulness results from the rise of centralized states that enforce a monopoly on the use of violence.
2) Prosperity makes lives more worth living and decreases our willingness to inflict death.
3) A progressive increase in knowledge about the world increases our willingness to accord moral status to others.
None of these seems to me to be very satisfactory, but they represent the current state of thinking on this important subject.
Third, how can general perceptions be so wrong? Pinker asks:
How could so many people be so wrong about something so important?Here there are several possible answers. I won't spoil them for you. Read Pinker's little essay for yourself here. I will, however, note his final point because it is both true and important. Our pessimism, born of a mistaken perception that the incidence of violence is rising, has led us to ask the wrong questions. Instead of asking why there is war, we should be wondering why there is peace. Instead of lamenting the things that go wrong, we should be trying to understand what it is that we are doing right?