A Shia militia sniper provides cover for Iraqi troops battling Islamic State fighters.

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Is the World Getting Safer? Maybe Not

Mark Buchanan, a physicist and science writer, is the author of the book "Forecast: What Physics, Meteorology and the Natural Sciences Can Teach Us About Economics."
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Is the world getting more peaceful? Some academics think so. New research, though, suggests they might be getting their math wrong.

Since 1945, armed conflicts between great powers have become much less frequent, and the annual number of fatalities has consistently declined. This has led some people -- among them the noted psychologist Steven Pinker, in his book "The Better Angels of Our Nature" -- to suggest that humanity may, perhaps, be growing out of war and moving into a more peaceful era. It's an idea that military historians find intriguing, and quite plausible.

Unfortunately, it may also be wishful thinking. Getting statistics right is hard, and it's especially hard when dealing with wars, which -- like earthquakes and financial markets -- follow a highly erratic pattern. Long periods of relative stability are punctuated by sudden, catastrophic events, such as World War II, which took the lives of millions. Statistically speaking, the data have "fat tails," meaning that a few observations account for most of the phenomenon being studied. As a result, indicators such as the average number of deaths per year can be misleading -- after any big event, things will always look like they're getting better.

To get a clearer sense of what’s really going on, the statistician Pasquale Cirillo, working alongside Nassim Taleb of "The Black Swan" fame, did an analysis using extreme value theory -- a branch of mathematics specifically designed for such problems. Looking at war data over 2,000 years, they found that violent conflicts have fatter tails than earthquakes and markets, suggesting an even more profound tendency to extremes. “History as seen from tail analysis,” Cirillo and Taleb conclude, “is far more risky, and conflicts far more violent than acknowledged by naive observation.”

Cirillo and Taleb also found no evidence that wars cluster together, as earthquakes and episodes of financial volatility are known to do. Rather, big wars follow no trend and simply occur with equal likelihood through time. Doing the statistics right, they argue, shows that the recent peaceful past is almost certainly causing us to seriously underestimate how much violent conflict we're likely see in the future. I've given some more technical detail on the argument here. Some of this has been known since the 1960s (I wrote about the topic in a book 15 years ago), and other recent studies have found similarly dissenting views. European economists Mark Harrison and Nikolaus Wolf, for example, have looked at the total number of bilateral conflicts between nations going back to 1870, finding that the total number of such conflicts has actually been increasing from then to the present. Indeed, the number of countries at war at any given time has steadily been rising.

To be fair to Pinker, his book was about a lot more than war. His point was that many forms of violence, including torture, homicide, slavery and violence against women, even cruelty to animals, have become less pronounced in modern times. Nothing in this new analysis runs against that. These trends may be real, and we can hope they continue. Wars, however, don't seem to be similarly in decline -- at least such a conclusion does not follow from careful mathematical analysis of the data.

Pinker and Taleb have squabbled over this topic in the past. Taleb critized and Pinker fired back. Although the new study should help clarify what the data on wars imply, it probably won't be the end of the debate.

This column does not necessarily reflect the opinion of Bloomberg View's editorial board or Bloomberg LP, its owners and investors.

To contact the author on this story:
Mark Buchanan at buchanan.mark@gmail.com

To contact the editor on this story:
Mark Whitehouse at mwhitehouse1@bloomberg.net