New research by the University of Warwick and Humboldt university shows that the frequency of wars between states increased steadily from 1870 to 2001 by 2% a year on average. The research argues that conflict is being fed by economic growth and the proliferation（增殖，扩散） of new borders. We may think the world enjoyed periods of relative freedom from war between the Cold War and 9/1 but the new research by Professor Mark Harrison from at the University of Warwick's the Centre for Competitive Advantage in the Global Economy, and Professor Nikolaus Wolf from Humboldt University, shows that the number of conflicts between pairs of states rose steadily from 6 per year on average between 1870 and 1913 to 17 per year in the period of the two World Wars, 31 per year in the Cold War, and 36 per year in the 1990s.

Professor Mark Harrison from the University of Warwick said:

"The number of conflicts has been rising on a stable trend. Because of two world wars, the pattern is obviously disturbed between 1914 and 1945 but remarkably, after 1945 the frequency of wars resumed its upward course on pretty much the same path as before 1913."

One of the key drivers is the number of countries, which has risen dramatically – from 47 in 1870 to 187 in 2001.

Professor Mark Harrison added:

"More pairs of countries have clashed because there have been more pairs. This is not reassuring: it shows that there is a close connection between wars and the creation of states and new borders. Besides, no matter how you divide it, we have only one planet. Our planet has already seen two world wars. As that experience suggests, you can never be quite sure what little conflicts will not suddenly snowball into much wider, more deadly struggles."

The fact that inspired the research is illustrated in the figure. The number of conflicts between pairs of states around the world has been rising since 1870. ("Pairwise conflicts" are measured by the number of pairs of countries in conflicts. Conflicts include everything from full-scale shooting wars and uses of military force to displays of force such as sending warships and closing borders.