… is from pages 179-180 of Mark Zupan’s 2011 Cato Journal paper, “The Virtues of Free Markets” (link added):
In his award-winning The Invisible Hand of Peace, [Patrick J.] McDonald (2009) undertakes a painstaking empirical analysis of hundreds of conflicts between nations over the past two centuries. He finds that the propensity of nations to promote free markets when it comes to matters of international trade is positively correlated with a reluctance to resort to war. Furthermore, a laissez-faire attitude with regards to international trade is a better predictor of peace than democracy. McDonald argues that this is because democracies still can be associated with systems of poorly defined private property rights that lead to greater zero-sum redistribution and unproductive rent-seeking. Waging war against other nations is but an extension of such a zero-sum mentality.


In his award-winning
