Interest groups' lobbying activity may contribute significantly to U.S. legislative polarization.

This paper analyzes bill-level data from 1999-2016 showing that bills lobbied by more non-profit interest groups have higher partisan polarization, measured as differences in voting percentages between parties.

🔍 Data & Methods

Using comprehensive datasets covering all federal bills and three state legislative bodies during the period.

This robust finding holds even after controlling for party agenda control or bill salience at the state level.

📊 Key Findings

• Floor votes on highly lobbied bills show greater partisan divergence (higher polarization scores)

• This relationship is evident across both federal Congress and select state legislatures

• The effect remains statistically significant when accounting for various factors influencing voting outcomes

💡 The Takeaway

The study argues that increased lobbying by non-profit interest groups helps explain the rising partisan division in U.S. politics during this period.