Information Is Beautiful displays the major causes of death throughout the 20th century (click to see the whole chart):
Steven Mazie takes a historical perspective:
The notoriously bloody 20th century was a lot less sanguinary than previous eras, when up to 15 percent of people lost their lives in violent conflicts. And things have gotten a lot better still since the end of World War II. Why the improvement? Pinker lists a host of positive influences, from rising IQs and the expansion of women’s rights to surges in global commerce and literacy. All these trends have pointed us away from the Devil and closer to the “better angels of our nature.”
And what is responsible for these trends? Governments! Good old-fashioned nation states, Weberian monopolies on violence. It turns out one of Hobbes’ central contentions was dead right: the most important function of political society, its primary mission, is to bring peace.