The Ideological Mapping of American Legislatures
American Political Science Review (August 2011), 105:3, pp. 530-551.
(with Nolan McCarty)
Aggregate Replication Data Download
Abstract: The development and elaboration of the spatial theory of voting has contributed greatly to the study of legislative decision making and elections. Statistical models that estimate the spatial locations of individual legislators have been a key contributor to this success (Poole and Rosenthal 1997, Clinton et al 2004). In addition to applications to the U.S. Congress, spatial models have been estimated for the Supreme Court, U.S. presidents, a large number of non-U.S. legislatures, and supranational organizations. But, unfortunately, a potentially fruitful laboratory for testing spatial theories of policymaking and elections, the American states, has remained relatively unexploited. Two problems have limited the empirical application of spatial theory to the states. The first is that state legislative roll call data has not yet been systematically collected for all states over time. Second, because ideal point models are based on latent scales, comparisons of ideal points across states or chambers within a state are difficult. This paper reports substantial progress on both fronts. First, we have obtained the roll call voting data for all state legislatures from the mid-1990s onward. Second, we exploit a recurring survey of state legislative candidates to enable comparisons across time, chambers, and states as well as with the U.S. Congress. The resulting mapping of America’s state legislatures has tremendous potential to address numerous questions not only about state politics and policymaking, but legislative politics in general.
A Bridge to Somewhere: Mapping State and Congressional Ideology on a Cross-Institutional Common Space
(with Nolan McCarty and Christopher Berry)
Published in the August 2010 issue of the Legislative Studies Quarterly
Aggregate Replication Data Download
Abstract:
Researchers face two major problems when applying ideal point estimation techniques to state legislatures. First, longitudinal roll-call data are scarce. Second, even when such data exist, scaling ideal points within a single state is an inadequate approach. No comparisons can be made between these estimates and those for other state legislatures or for Congress. Our project provides a solution. We exploit a new comparative dataset of state legislative roll calls to generate ideal points for legislators. Taking advantage of the fact that state legislators sometimes go on to serve in Congress, we create a common ideological scale. Using these bridge actors, we estimate state legislative ideal points in congressional common space for 11 states. We present our results and illustrate how these scores can be used to address important topics in state and legislative politics.
Congressional Voting by Spatial Reasoning
(with Jon C. Rogowski)
Working Paper
Version: May 9, 2012
Abstract:
While the spatial model remains the dominant paradigm for modeling the behavior of both voters and candidates, attempts to test its key assumptions and core predictions empirically have been hindered by three problems. First, the main tools measuring ideology in public opinion have historically been flawed. Second, sufficient data have generally not been available to characterize the ideologies of losing candidates. Finally, we lack a common scale on which to place both constituents and candidates. We solve these problems with a new empirical approach. We estimate public ideology via a large battery of issue preference questions asked of tens of thousands of respondents in the 2000 and 2004 National Annenberg Election Studies, the 2008 CCAP survey, and the 2010 CCES survey. On the candidate side, we employ Project Vote Smart surveys (a state and congressional candidate survey administered since the early 1990s) to obtain estimates of electoral platforms for both winning and losing candidates. A sizable number of substantively identical questions appear on both the candidate and voter surveys, which allows us to jointly scale estimates of candidate and voter preferences. Using these data, we assess the extent to which voters choose candidates in ways that are consistent with spatial reasoning, and investigate how individual-level factors condition these processes. This project produces the largest sample to date of preference estimates that are comparable across constituents and elected officials. We find strong and consistent evidence that vote choice in congressional elections is strongly associated with spatial proximity. We also find that independents and better-informed voters are more sensitive to spatial proximity than partisans and voters with lower levels of education. These results have important implications for theories of voter decision-making and electoral and representative institutions.
A Primary Cause of Partisanship? Nomination Systems and Legislator Ideology
Working Paper
Abstract: Many supporters of political reform advocate opening party nominations to non-members as a way of increasing the number of moderate elected officials. This presumes that the composition of the primary electorate is, in fact, a significant cause of polarization, an idea that has rarely been tested empirically. We marry a unique new data set of state legislator ideal points to a detailed accounting of primary systems to gauge the effect of primary systems on polarization. The results of this analysis suggest that the openness of a primary election has little effect, if any, on the partisanship of the politicians it produces. We speculate on why the effect is so inconsistent and weak, and discuss the implications of our study for the theoretical literature on parties in American political life.
The Causes and Consequences of Party Switching in American State Legislatures
Working Paper
Abstract: The influence of parties is a perennial topic for debate. Do parties affect their member’s revealed preferences, or do they merely reflect them? Attempts to isolate party effects are fraught with inference problems. Using the natural experiment afforded by legislators switching parties, previous studies such as \cite{Nokken:2000, Nokken:2004} measure preference shifts. Assuming personal preferences to be constant, these shifts are held to reflect party pressure. The problem is that, due to the focus on Congress, only a miniscule number of modern cases exist, and institutional variation is minimal. Consequently, inferences drawn are not as strong. We use a new, original data set of state legislator ideology in 50 states from 1993-2008, drawing from roll call votes and legislator surveys. These ideal point estimates are in common space for cross-state comparability. We find nearly 170 party switchers at the state level, dwarfing by nearly five times that for postwar Congresses. We analyze the degree of ideological change revealed by party switchers, as well as their incidence.
All Together Now: Putting Congress, State Legislatures, and Individuals in a Common Ideological Space
Working Paper
Abstract: Two problems hinder the ability of scholars to assess the quality of representation of state-level public opinion by elected representatives. First, the main tool measuring ideology in public opinion has historically been self-reported, but this is now well known to be severely plagued by measurement error. Second, and far more binding, we lack a common scale on which to place both constituents and representatives. While the literature has addressed a number of methods estimating a common space for politicians’ ideal points across political institutions, little work exists that incorporates citizens into this space. The unified methodology in this paper solves both problems in order to assess representation of constituents by their congressional delegations \emph{and} state legislatures. Bridging is accomplished using policy preference questions from a state and congressional candidate survey administered since the early 1990s. I ask those questions in my own 2008 survey of over 4,200 citizen respondents, representative at the state and national levels. Thus, citizens, state legislators, and members of Congress can be located on the same ideological scale. Since small states still have too few respondents to be useful, I employ multilevel regression with poststratification to model state-level public ideology and obtain estimates for all 50 states. I find that both congressional delegations and state legislators–both strikingly polarized–systematically under-represent large portions of their constituents. Finally, I employ the new common space scores in a new test of the spatial voting (proximity) model for congressional elections, and find that my measures of ideology compare favorably to alternatives.
Methodological Issues in Bridging Ideal Points in Disparate Institutions in a Data Sparse Environment
(with Nolan McCarty and Christopher Berry)
Working Paper
Abstract: In earlier work, we created Congressional common space scores for multiple state legislatures using bridge actors who served in both institutions. Here, we employ simulations to explore the general issues involved in bridging institutions in data-sparse environments, where only a few bridge actors exist to allow inter-institutional comparisons. We find that only a few such bridges are necessary to improve ideal point estimates of rescaled legislative chambers.
European National Parliaments in European Parliament Common Space
Abstract: Numerous attempts have been made to put European political parties on a common ideological scale, including content analysis of political statements, hand coding of party manifestos, and surveys of expert opinion. At the same time, there have been numerous attempts at using roll call-based ideal point estimation techniques on national and transnational parliaments. These have the satisfying property of using newly available roll call data, which due to their presumed consequentiality may reveal latent preferences better than other methods. However, we cannot compare within-state parliament estimates to those of other countries or the European Parliament. The solution to the problem lies in the existence of bridge actors–in this case, substantial numbers of national parliamentarians who also serve in the EP before and after their national service. Their revealed preferences in the form of roll call votes on the European Parliament’s agenda allow us to rescale solely national members of parliament with a common space score. I test this approach with roll call data on several national parliaments and all sessions of the EP. The common space estimates allow me to explore important questions in comparative politics.
