In this paper, I conduct an empirical assesment of Olson and Zeckhauser's 1966 Economic Theory of Alliances. Olson and Zeckhauser argue that alliances are subject to a collective action problem. Larger alliance members will bear a disproportionate share of the burden of providing security.
While the concept of free-riding is often invoked in discussions of alliance politics, there is little solid empirical evidence for or against Olson and Zeckhauser's model. I rectify this gap in knowledge by estimating the correlation between economic weight and military spending for 285 alliances. This model finds little evidence that increasing economic weight in an alliance leads to higher military spending, as the public goods model would expect.