Comparing Ideal Points Across Institutions and Time

Abstract

Many spatial theories of policymaking in the context of a system of checks and balances require the estimation of ideal points which are comparable across institutions. This analysis evaluates comparisons between the president, Senate, and House. For applications which presume that legislators change their positions over time, the most commonly used estimates impose too many restrictions on the ideal points. I consider an alternative approach to creating a common scale by using interest groups (American Conservative Union [ACU] and Americans for Democratic Action [ADA]) as reference actors and incorporating "bridge votes," roll calls on which the House and Senate vote on identical text. The analysis demonstrates this approach can produce comparable estimates across time and chamber.