We consider the historical development of a characteristic crucial for the functioning and normative appeal of Westminster systems: cohesive legislative parties. To do this, we gather the universe of the twenty thousand parliamentary divisions that took place between 1836 and 1910 in the British House of Commons, construct a voting record for every Member of Parliament serving during this time, and carry out analysis that aims to both describe and explain the development of cohesive party voting. In line with previous work, we show that -- with the exception of a chaotic period in the 1840s and 1850s -- median discipline was always high and increased throughout the century, with an obvious uptick around 1868. We use novel methods to show that much of the rise in cohesion results from the elimination of a rebellious "left tail" from the 1860s onwards, rather than central tendency shifts. In explaining the aggregate trends, we use panel data techniques to show that there is scant evidence for "replacement" explanations that involve new intakes of members behaving in more disciplined ways than those leaving the chamber. We offer evidence that more loyal MPs were more likely to obtain ministerial posts, and speculate that this and other "inducement"-based accounts offer more promising explanations of increasingly cohesive parties.
This is joint work with Andrew C. Eggers.
