Why did U.S.-assisted counterinsurgency (COIN) efforts succeed in the Philippines in the 1950s yet falter in Vietnam a decade later? Why were counterinsurgents able to score a quick victory in Venezuela in the early 1960s but confronted by a long and bloody conflict in El Salvador in the 1970s and 1980s? In seeking to answer these questions, this article provides theoretical motivation for the oft-made claim that U.S. counterinsurgency strategy has been most effective in countries in which the local government engaged in meaningful political and economic reforms to address a population's grievances. What determines whether a government is likely to engage in a reform process? The article proposes that reform is a function of the economic structure of elite assets. When assets are immobile and highly concentrated in one sector, as in heavily agricultural societies like Vietnam or El Salvador, redistributive reforms will prove more difficult, and counterinsurgency efforts will struggle as a result. Conversely, in countries in which the structure of elite assets is more diversified, reforms will prove more feasible, making it easier to undermine an insurgency's popular appeal.