Really pleased that my paper with @jcrohsaine and @GeoffLorenz is out in #FirstView at @apsrjournal today.

A THREAD on our findings: https://twitter.com/CUP_PoliSci/status/1283360692486262784

We use interest groups public positions on legislation collected by @MapLight to estimate common space preference ideal points for over 2,600 interest groups and 950 members of Congress between 2004-2016 via bayesian IRT. We uncover what we term, "polarized pluralism"

We argue that interest groups are polarized along a single highly explanatory dimension, in a manner that is similar to Members of Congress. Note: because our estimates include positions taken by IGs on bills which never get a vote, IG scores are less shaped to agenda setting.

We observe substantive heterogeneity in revealed preferences both across & within industry sector and organization type. This suggests that studies of interest groups that rely on group typologies as a proxy for interest position or diversity don't capture true interest diversity

Only by drilling down to very specific single issue categories do we observe anything approaching within-type homogeneity of preference

Finally, we turn to how different activities by interest group may distort the overall distribution that legislators perceive, by weighting the joint posterior distributions by level activity.

1) Organizations that take the most positions are even MORE polarized!

2) Organizations that make campaign finance contributions through their PACs, are more polarized still, and we there is considerable over-representation of conservative interests/positions

3) Weighting the joint posterior distribution by lobbying expenditures reveals the distribution which is most substantively distorted from the unweighted distribution

Almost ALL of the mass of the distribution is right of center when accounting for lobbying spending.

Together this work reveals:
1) interest group position taking is well captured by a single preference dimension
2) substantive heterogeneity both within and across group type
3) patterns of polarization which mimic other elite actors
4) rightward shift in $$ weighted activity