"Using supercomputers, the authors have analysed 16 million individual roll call votes since the two Houses of Congress began recording votes in 1789. By tracing the voting patterns of Congress throughout the country's history, Poole and Rosenthal find that, despite a wide array of issues facing legislators, over 80 per cent of a legislator's voting decisions can be attributed to a consistent ideological position ranging from ultraconservatixm to ultraliberalism."@en
"In this wide-ranging and innovative study, Keith T. Poole and Howard Rosenthal use 200 years of congressional roll call voting as a framework for a new interpretation of important episodes in American political and economic history. Despite the wide array of issues faced by legislators over the past two hundred years, the authors have found that over eighty percent of a legislator's voting decisions can be attributed to a consistent and predictable ideological position ranging from ultraliberalism to ultraconservatism. Using a simple geometric model of voting, the authors shows that roll call voting has a very simple structure and for most of American history roll call voting patterns are very stable. This stability is based upon two great issues - the extent of government regulation or intervention in the economy, and race."

Congress a political-economic history of roll call voting