Here are some of the details that you may be curious about.
Why does the Acadie–Bathurst riding in New Brunswick include elections 31 (held in 1979) to 43 (held in 2019) while Avalon only includes elections 38 (held in 2004) to 43?
Canada adjusts riding boundaries and sometimes the number of ridings every 10 years – after each census. If the change is dramatic enough, the riding name changes at the same time. For example, Madawaska–Restigouche was created in 1996 by combining parts of the Madawaska–Victoria and Restigouche–Chaleur ridings (which ceased to exist).
Time-based analysis like the Parity Across Time project benefits from longer time periods. So the time-lines for ridings were extended as in the following example of “Toronto Centre”.
The riding of “Toronto Centre” spans elections 38 to 43. The riding of “Toronto Centre–Rosedale” spans elections 36 to 37. Bill Graham was the winner in Toronto Centre–Rosedale in election 37 and also won in Toronto Centre in election 38. So we think of Toronto Centre as the successor riding to Toronto Centre–Rosedale and treat them, in this analysis, as the same “extended riding”. An extended riding uses the most recent name.
It so happens that the riding of “Rosedale”, which spans elections 18 to 35, was
won by the same person who won Toronto Centre–Rosedale in election 36.
So the extended riding of Toronto Centre is viewed as the successor riding of Rosedale and Rosedale is added on as well.
There are some ridings that span all 43 elections without name changes (for example, Simcoe North, Beauce, and Sherbrooke). One, Montmagny–L’Islet–Kamouraska–Rivière-du-Loup, spanned six name changes as described above.
An extended riding was only included in this analysis if it spanned at least four elections and included the most recent election. 106 ridings (out of 338) did not meet this criteria.
How do we group voters and compare that to who won? Political parties are the most obvious answer but even this presents challenges. Parties have changed name and merged over the years. For example, consider the Progressive Conservative party merging with the Canadian Alliance to form the Conservative Party of Canada.
Each party was assigned a single “ideology code” and whether or not it was a “mainstream” party. It’s these ideology codes for mainstream parties that are shown on the graphs. Mainstream parties are defined as parties who earned at least five percent of the vote in any election. See the Party summary in the Raw Data section of the web site for more information.
For currently sitting MPs, the time spent representing their constituents is calculated to the date the graphs were generated. This date is available beneath the table following each graph.