‘’We consider the meaning and measurement of electoral competitiveness in a mature, parliamentary democracy. Devising a practical and useful measure of the competitiveness of an economic market is not an easy task, and doing so for an election contest is no less challenging. This is so despite the common use of such indexes as the effective number of parties and first versus second place vote margins. Our analysis highlights both differences and similarities among the indexes used to measure the competitiveness of economic markets and those used to measure the competitiveness of electoral contests. Working at both the constituency and the national party level, we apply the various indexes to measure electoral competitiveness across Canadian federal elections using the complete record of regular constituency level elections from Confederation in 1867 to the 41st election in 2011. Finally, in lieu of substantive conclusions, we pose some key questions that we think we need to address in further work. This preliminary paper is a part of a larger project on the meaning, measurement and consequences of electoral competitiveness in mature democracies. ‘’