#  Sooahn Shin (Workshop in Applied Statistics) 

 



####  calendar\_today Date and Time 

 **September 18, 2024** 

 12:00PM - 01:30PM EDT 

####  pin\_drop Location 

 **CGIS Knafel room K354, or virtual via Zoom**  



 

 



 

##  Today's Speaker

 Sooahn Shin (Department of Government), "Measuring Issue Specific Ideal Points from Roll Call Votes"

##  Abstract

 Ideal points are widely used to measure the ideology and policy preferences of political actors, ranging from voters and legislators to sovereign states. Yet, an outstanding challenge is to estimate ideal points specific to a single issue area. The conventional approach resorts to subsetting voting data, which results in the loss of valuable information and makes comparisons across issue areas ambiguous. To address this, I introduce IssueIRT, a hierarchical Item Response Theory (IRT) model that uses roll-call votes and user-supplied issue labels to estimate issue-specific axes, each running from left to right positions. This approach first estimates multidimensional ideal points using all available voting data, which are then projected onto issue-specific axes to generate single-dimensional, issue-specific ideal points. Furthermore, I develop a measure of issue similarity to compare the alignment of different issue areas on a unified left-to-right spectrum. I demonstrate that IssueIRT effectively captures issue-specific voting behaviors through simulations and applications studies. Specifically, I show cross-party, regional division over monetary policy in the US House of Representatives during the depression of the 1890's. Finally, I show that polarization in Congress has markedly increased across 32 separate issues from 1979 to 2023. The R package issueirt is available for implementing IssueIRT.

 *The Applied Statistics Workshop (Gov 3009) meets all academic year, Wednesdays, 12pm-1:30pm, in CGIS K354. This workshop is a forum for advanced graduate students, faculty, and visiting scholars to present and discuss methodological or empirical work in progress in an interdisciplinary setting. The workshop features a tour of Harvard's statistical innovations and applications with weekly stops in different fields and disciplines and includes occasional presentations by invited speakers.  
  
All interested Harvard affiliates are invited to attend.*



 

 



 

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