Mixed-member proportional electoral systems are characterised by having two types of members of parliament (MPs): district MPs elected directly in a district and list MPs elected via a party list. While it has been suggested that district MPs have a more prestigious and safe position than list MPs, little is known about possible differences between list and district MPs in terms of the length of their parliamentary careers.
New statistical analyses by IMI MIRA Beate Ehrhardt, Professor Hilde Coffé (Dept of Politics, Languages & International Studies) and Josh Givens (PhD student, CDT in Computational Statistics and Data Science, University of Bristol) show that it is beneficial for the career length of members of parliament (MP) to be a district MP in contrast to a list MP. However, when list MPs ‘move on’ to becoming district MPs during their parliamentary career, they have the longest careers of all MPs.
Using data on all New Zealand parliamentary elections between 1996 and 2017, the authors investigate to what extent the mode in which MPs are elected throughout their careers relates to the length of their careers. This is an excellent showcase for the power of a multivariate Cox Proportional-Hazards analyses: we estimate the impact of career patterns on the probability not to be re-elected over time while controlling for known effects like gender, age and ethnic background.