Bicameral Distinctiveness in American State Legislatures.

Many important traits of state legislatures vary across chambers within a state. Yet according to existing typologies in the comparative study of bicameralism, the 49 bicameral American state legislatures would be deemed quite homogeneous. To resolve this disjuncture, I identify a novel dimension of bicameralism that distinguishes among state legislatures by capturing the extent to which the two chambers serve as meaningfully different venues for influence. Based on this framework, I develop an index of bicameral "distinctiveness" rooted in three traits that speak to policy influence across chambers: the ratio of seats, bipartisan representation, and constituency dissimilarity. This measure reveals sizable variation across states and a conspicuous geographic pattern, with considerably greater bicameral distinctiveness in the Eastern United States. In turn, I assess the construct validity of this measure, showing how patterns of second chamber bill amendment vary systematically with the level of bicameral distinctiveness. [ABSTRACT FROM AUTHOR]