A New Measure of State Government Ideology, and Evidence that Both the New Measure and an Old Measure Are Valid

Abstract We modify Berry et al.‘s congressional-delegation-based measure of state government ideology to construct a new measure—which we call the state-legislative-based state government ideology measure—by relying on Shor and McCarty's National Political Awareness Test common space estimates of the ideal points of U.S. state legislators. We conduct tests of convergent and construct validity for the two measures. We find that they correlate highly in each year for which the state-legislative-based indicator is available (1995–2008), and when observations are pooled across all years. We also replicate numerous published studies assessing the impact of state government ideology using each indicator of ideology and find that the two measures nearly always yield similar conclusions about the effect of government ideology. Because the state-legislative-based measure is based on more direct estimates of the ideal points of state legislators than is the congressional-delegation-based measure—which uses estimates of ideal points for members of Congress from the same state as a proxy—we believe the state-legislative-based measure is superior, and we recommend that scholars use it when it is available for the state-years being studied. Because our empirical evidence indicates that Berry et al.‘s congressional-delegation-based measure is also valid—and it is available for a much longer period (annually beginning in 1960)—we advise that it be used when the state-legislative-based measure is not available.