A New Method for Measuring Legislative Content and Change

This article has four purposes: (1) to show that it is important to develop a satisfactory way to conceptualize and measure legislative content and change; (2) to propose criteria for evaluating measurement procedures, show that past approaches are inadequate, and propose an improved approach; (3) to apply the approach to voting by the U.S. Senate on Vietnam-related roll calls, 1964-1973; (4) to assess the validity of the approach. The proposed approach involves defining the relevant universe of content more narrowly than in most previous work and using Smallest Space Analysis to derive dimensions and locate items on them. A substantively interpretable three-dimensional solution is found, and the scores given legislative items behave statistically in ways that would be expected of valid measures.