Four pure types of legislative organization are characterized as data generating processes for commonly used measures of preferences or, in the spatial vernacular, ideal points. The types of legislative organization are differentiated by their partisan versus nonpartisan nature of agenda...

Credible tests of hypotheses about power require credible measures of power. Roll rates purport to measure the relative power of the parties in legislatures. This article develops and employs a baseline model to assess roll rates. Although on the surface roll rates have some intuitively...