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Insights from the Field

AdaBoosted Trees Improve Supreme Court Forecasts—and Predict Wars and Vote Shares


AdaBoost
Decision Trees
Supreme Court
Civil War
Elections
Law Courts Justice
Pol. An.
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Dataverse
Improving Supreme Court Forecasting Using Boosted Desicion Trees was authored by Aaron Kaufman, Peter Kraft and Maya Sen. It was published by Cambridge in Pol. An. in 2019.

🔎 Why This Matters

Boosted decision trees are widely used in machine learning but remain underused in political science, despite offering many useful properties for prediction. This article explains how one variant—AdaBoosted decision trees (ADTs)—can be applied to social science forecasting and demonstrates its value on several familiar political prediction problems.

🔧 What the Article Does

  • Explains the mechanics and practical implementation of AdaBoosted decision trees (ADTs) for social-science prediction tasks.
  • Illustrates the approach with three applied forecasting problems:
  • U.S. Supreme Court rulings
  • Onset of civil wars
  • County-level vote shares in U.S. presidential elections

🧭 How the Method Was Applied

  • Describes an ADT workflow tailored to political data, highlighting how to prepare inputs, train boosted classifiers/regressors, and evaluate out-of-sample prediction performance.
  • Emphasizes ADTs as a variant of boosted decision trees commonly used in machine learning and shows how they can be adapted to standard political-science datasets and questions.

📈 Key Findings

  • The ADT approach outperforms existing predictive models in the well-known task of forecasting U.S. Supreme Court rulings.
  • Additional examples illustrate the ADT approach on civil-war onset prediction and on modeling county-level presidential vote shares, showing the method’s applicability across different types of political outcomes.

🔍 Implications for Research and Practice

  • ADTs offer a practical, high-performing tool for political-forecasting tasks, encouraging wider adoption of boosted-tree methods in political science.
  • The article provides a clear, reproducible template for applying AdaBoosted decision trees to diverse political datasets, lowering the barrier for researchers and analysts seeking improved predictive performance.
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