🔎 What This Study Does

This study compares party systems inside bicameral legislatures by using newly available data on upper‑chamber elections. It examines two dimensions of inter‑chamber similarity: partisan congruence (how similar party composition is between lower and upper chambers) and a new measure, nationalization congruence (how similar the geographic or national reach of parties is across the two chambers). The analysis traces how these forms of congruence vary across countries and over time and links them to the power of the upper chamber (symmetry).

📊 New Upper‑Chamber Election Data and Measurement Approach

• Uses recently released data on upper‑chamber elections to map party composition in both chambers.
• Introduces a novel metric that captures differences in party nationalization between upper and lower chambers (nationalization congruence).
• Retains a standard measure of partisan congruence to compare composition directly across chambers.
• Investigates variation across countries and over time to situate findings in comparative perspective.

🔍 Key Findings on Congruence, Symmetry, and Spending

• The power of the upper chamber (symmetry) is systematically associated with both partisan and nationalization congruence.
• The interaction between congruence and symmetry shapes policymaking: when bicameral systems are symmetric, partisan and nationalization congruence can have contrasting effects on government spending patterns.
• In asymmetric bicameral systems, both forms of congruence have negligible implications for government spending.

⚖️ Why It Matters

• Demonstrates that bicameral power structures alter how inter‑chamber party alignment translates into policy outcomes, especially fiscal policy.
• Highlights the importance of measuring not just party composition but the national reach of parties across chambers to understand legislative dynamics.
• Offers a new comparative tool for scholars and analysts studying bicameralism and its consequences for governance and spending.