The impact of individual and collective performance on ministerial tenure

Government ministers in Parliamentary democracies are career politicians for whom public service is an important source of motivation. The length of their tenure is controlled by the Prime Minister. We test a simple Principal-Agent model of parliamentary government in which the Prime Minister evaluates her ministers according to information available to her that is related to their performance. We study the effects of individual and collective ministerial performance on the length of time a minister serves in British government over the period 1945-97. We use the number of resignation calls for a minister as an individual performance indicator and the cumulative number of such calls as an indicator of government performance. A minister's hazard rate increases sharply after the first individual call for resignation and is decreasing in the cumulative number of resignation calls. These results are consistent with the Principal-Agent model and with the use of relative performance evaluation by the Prime Minister.