Toward Measuring Free-Riding: Counterfactuals, Alliances, and US–Philippine Relations


 Do allies free ride? Although plausible, the concept of free riding relies upon a counterfactual: if the ally did not have a powerful patron, then it would invest more in its own defense. However, these claims are often asserted, not shown. The concept of free riding, although influential in the field of security studies, is almost unfalsifiable. In this article, we show logically how difficult it is to ascertain actual free riding. Rather than dismiss the entire concept, however, we attempt to provide two hypotheses and one scope condition that moves closer to a direct assessment of claims of free riding: first, if the ally is free riding, as the patron's commitment decreases, the ally should spend more on its own defense; second, all things being equal, a state with a powerful patron should spend less than one without. The key scope condition is whether the ally cares sufficiently about the issue to fight. We use the case of East Asia—and in particular the Philippines—to illustrate these dynamics. We conclude that the low defense spending of US allies and non-allies in East Asia is not free riding but rather a reflection of their low threat perceptions.