One school of thought in international affairs theorizes that globalization is good for peace and security, and that increased economic interdependency will decrease the likelihood of war. Likewise, some think that the proliferation of democracy makes peace more likely. However, both propositions continue to be debated by academics and foreign policy observers.

A 2011 study published in Economic History Review, “The Frequency of Wars,” reviews data relating to the frequency, causes and types of conflicts since 1870, and examines how often wars have occurred, why and in what form. The researchers, from the University of Warwick and Humboldt University, use broad criteria in counting conflicts; they include any pairs of countries that have “disputed with each other,” and this category “includes displays as well as uses of military force.”

The study’s findings include:

• There were 3,168 conflicts between 1870 and 2001. There has been a steady upward trend in the number of bilateral conflicts over this period — about 2% annually on average. Russia/USSR originated the most conflicts (219). The next five countries, in order, are: the United States (161); China (151); the United Kingdom (119); Iran (112); and, Germany (102).
• The pattern over this time has been uneven and influenced by the birth of new nations — from about 50 to more than 180 over the period in question: “In the first 80 years the number of countries did not change much; the relative frequency of disputes fluctuated wildly and tended to rise. Then, over the next half century, the relative frequency of disputes fell back to the level of the 1870s and below, but the number of countries increased dramatically and this took over as the main driver that kept the absolute number of conflicts on its upward trend.”
• The characteristics that make countries more potentially bellicose are difficult to pin down: “The rising frequency of bilateral conflicts is reflected right across the global distributions of countries by size and wealth. Wealthier countries have not been responsible for more than their share of military interventions. If their share has risen over time, it is at a rate that is all but imperceptible.”
• The beginning of the 21st century resembles the period of the 1910s: “Evidence suggests that, normalized by the number of countries in the world, the risk of war is lower today than at the end of the 19th century. Normalized by the number of planets we have to share, however, it is of the same frequency (if not intensity) as during World War I.”
• Over specific and large sub-periods of time (1870-1913 and 1970-2001), increased global economic openness and democratization were strongly associated with increased absolute frequency of wars.

The study’s authors conclude by noting that the “demand for statehood is also a demand for the capacity to engage in national self-determination by force, and each new state has added a focus for potential conflict. With the downfall of empires, moreover, democracy has become more typical — and, with democracy comes improved fiscal capacity. As a result, countries that adopt democracy are likely to be able to raise taxes or borrow more in order to promote national adventures without recourse to domestic repression.”