Measuring Foreign Policy Positions of Members of the US Congress

Studies have shown that a foreign policy position of a member of Congress is often distinct from a domestic one. Despite this, measures commonly used to determine the foreign policy positions of members of Congress are based on congressional votes on domestic as well as foreign policy matters. As foreign policy votes take up only a small portion of all congressional votes, these measures conflate a member’s foreign policy position with his or her domestic policy position. While there are other measures based exclusively on foreign policy votes, these are also problematic because they tend to use a small number of controversial votes and thus inflate extremism. To address these shortcomings, I present a new measure by applying a Bayesian item response theory model to all foreign policy votes. This paper demonstrates the similarities, differences, and advantages of this measure by comparing it with the existing measures in a series of analyses of foreign policy positions of political parties and individual legislators.