🔎 The Puzzle:

Many traits of state legislatures differ across chambers, yet existing comparative typologies treat the 49 bicameral American state legislatures as largely homogeneous. This research identifies a new dimension of bicameralism that captures how much the two chambers function as meaningfully different venues for influence.

📊 How Distinctiveness Is Measured:

A composite index of bicameral distinctiveness is developed and rooted in three measurable traits tied to policy influence across chambers:

• the ratio of seats between chambers, reflecting size and institutional weight
• bipartisan representation differences, capturing party composition contrasts
• constituency dissimilarity, measuring how different the electorates and districting are across chambers

The index is applied across all 49 bicameral U.S. state legislatures.

📈 Key Findings:

• The index reveals sizable variation in bicameral distinctiveness across states.
• A clear geographic pattern emerges: substantially higher distinctiveness in the Eastern United States.
• These patterns challenge typologies that portray American state bicameralism as homogeneous.

🔬 Evidence of Validity:

Construct validity is assessed by linking the index to legislative behavior. Patterns of second-chamber bill amendment vary systematically with levels of bicameral distinctiveness, supporting the measure's relevance to interchamber influence.

📌 Why It Matters:

This measure provides a precise, empirically grounded way to distinguish among U.S. bicameral legislatures. It offers a new tool for studying how chamber design and representation shape policy influence, legislative strategy, and comparative assessments of bicameralism.