The 20th century was the bloodiest in human history. In Humanity: A Moral History of the 20th Century, Jonathan Glover estimates that 86,000,000 people died in wars fought from 1900 to 1989. That means 2,500 people every day, or 100 people every hour, for 90 years.

In addition to those killed in war, government-sponsored genocide and mass murder killed approximately 120,000,000 people in the 20th century—perhaps more than 80,000,000 in the two Communist countries of China and the Soviet Union alone, according to R. J. Rummel's Statistics of Democide.