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Mapping State and Congressional Ideology

Boris points us to this paper (with Christopher Berry and Nolan McCarty):


Boris writes:

Estimated congressional common space scores for four states compared with scores for the US House, 1996-2006 (unique legislators in this time period). Colored numbers under density plot indicate party medians (red are Republicans), the black number on the x-axis is the bichamber median. Short bars are 10th and 90th party percentiles. Party overlap statistics are reported in the legend.

Note how similar CA and MI look to the House in terms of party polarization, and how different PA and especially FL look.

And here’s the abstract:

Two major problems exist in applying ideal point estimation techniques to state legislatures. First, there has been a scarcity of available longitudinal roll call data. Second, even where such data exists, scaling ideal points within a single state suffers from a basic defect. No comparisons can be made across institutions, whether to other state legislatures or to the US Congress. Our project is a solution to both of these dilemmas. We use a new comparative data set of state legislative roll calls beginning in the mid-1990s to generate ideal points for legislators. We then take advantage of the fact that state legislators sometimes go on to serve in Congress to create a common ideological scale between Congress and the various legislatures. These “bridge actors” are similar in concept to members of the House who go on to serve in the Senate, thereby providing the “glue” necessary to scale the House and Senate together. We have successfully prototyped this approach for California, Pennsylvania, Michigan, and Florida. Using these bridge actors, we create a new state-federal congressional common space ideological scores. We conclude by using these common space scores to address important topics in the literature.

Cool. This is sort of like those things where people compare Babe Ruth to Mike Schmidt, or whatever: Ruth played with Gehrig, who played with etc etc., going up to the present time. I guess the next thing to do is check that the “bridge actors” identified by Shor et al. are not systematically different than other legislatures, for example, in changing their attitudes when moving up to the big House.

I have no substantive comments right now, but I’ll follow up on Boris’s invitation and comment on the graphs:

Fig 2,3: These are pretty, but make the symbols much smaller. Little dots would be fine. Also, if you really don’t want to use the now-conventional red and blue coloring, then just pick two completely different colors (e.g., green and purple). Don’t just use red and blue in the opposite way!

Fig 4,5: Do these as a 4×2 grid of graphs and put the graphs on a common scale.

Figs 6,7: You have 3 plots for each state. Do these as a grid of graphs with 3 columns.

Fig 8,9,10: Again, consider as a single display with 3 columns

I’d also like to see some graphs of raw data if that’s possible.


  1. NU says:

    Re: Figs 2 & 3, they don't just appear to be just reversing the conventional colors — they are using them inconsistently! E.g., "MI only" in Fig. 2 and "MI and House" in Fig. 3 use blue for Democrats and red for Republicans, in contrast to all the other subfigures.

  2. Bob O'H says:

    The abstract is awful:

    Two major problems exist in applying ideal point estimation techniques to state legislatures.

    Well, you could use Google Earth to pin-point them. If that isn't accurate enough, use GPS.

    Or are they measuring something else? Colour coordination? Attendance? Aaagh, I don't want to guess, I want the abstract to tell me!

    Grumble, grumble…


  3. Bob O'H says:

    Aagh, sorry about the formatting: it looked different in the preview…


  4. Boris S. says:

    NU: sorry for the inconsistency, but it's a draft!

    Bob: not sure what you mean about the sentence in the abstract.