Don Boudreaux links to an interesting working paper by Columbia University political scientist Erik Gartzke; The Capitalist Peace.
The following is the conclusion of the paprer.
“This study offers evidence suggesting that capitalism, and not democracy, leads to peace. Additional research is needed to corroborate, extend, and even refute the findings reported here. One must be circumspect in questioning a body of evidence as large and as carefully constructed as that on the democratic peace. Still, economic liberals have long seen in free markets and prosperity the potential to discourage war. A century ago, the “conventional wisdom” looked more like this study and less like that of democratic peace researchers. While past arguments were clearly simplistic and overblown, there does now seem to be grounds for reconsidering liberal economic peace theory.
Critics can differ with my revision of classical arguments, or can plausibly challenge the assumptions on which my version of the capitalist peace is built. The statistical models I develop, and the findings that I present, can be altered, possibly in ways that again show that democracy matters. For now, I hope my claims are coherent, empirically plausible, and at the very least intellectually provocative. What is the “larger” relationship between development, capitalism, and democracy? It might be that democracy actually lies behind the apparent impact of capitalism on peace. Still, the world was not always made up of 50% democracies. Little attempt has been made to rule out the possibility that democracy and peace have common causes. A logical extension of this study is the exploration of determinants of political and economic liberalism, though resolving these more complex causal arrows would seem to require a far more profound set of conclusions about the world, ones that are still under construction in comparative politics, economics, and other fields.