Between October 22nd and November 30th British Columbians will vote on whether to adopt a new electoral system. In a series of posts, I am looking at the level of proportionality and the level of regional representation that each system produces. In previous posts I looked two versions of mixed member proportional (here and here) and dual member proportional. In the post I will look at rural urban proportional. Rural urban proportional systems produce results that match parties’ votes in different regions reasonably well. The extent to which they are proportional varies from election to election. Like in mixed member proportional systems that use only region-wide vote shares, these systems have the potential to create province-wide disproportionality.
Rural urban proportional representation is really two systems instead of one. Under this system, urban areas of the province would use single transferable vote (STV). In this system, multi-member ridings are created. For my simulations, I created multi-member ridings in the Victoria area, Vancouver, the Lower Mainland, and the Okanagan. The ridings that would be created in reality if this system were adopted would be decided by a boundaries commission and have yet to be determined. The more members each riding has, and the larger each riding is, the more proportional the result will be. I created ridings with between 4-7 members by putting together existing BC ridings. For a breakdown of which first past the post ridings fit into which STV ridings see the PDF below. Parties can run as many members in a riding as there are seats, though it is often not in their strategic interest to do so. Voters then rank order candidates and are allowed to either rank members of the same party together (for example a Liberal, another Liberal second, and so on) or intersperse candidates from different parties. It is, however, in the strategic interest of voters that wish to see a particular party do well to rank candidates from their preferred party together.
To be elected under STV, candidates must win enough votes to cross a threshold determined by the follow formula: threshold =(votes/(number of seats in the riding +1))+1. If a candidate crosses the threshold, any votes beyond what they needed to cross the threshold get redistributed to their voters’ second choices. If that does not lead any other candidates to get elected the last place candidate is eliminated and that candidates’ voters are redistributed to those voters’ second choices. This process repeats until all seats are filled. For the CGP Grey video explanation of how this system works, check out this link.
In rural urban proportional, rural areas of the province would use a mixed member proportional system. A province-wide rural list system would produce a more proportional result, but the Attorney General’s report suggests that seats in the system would be assigned based on the share of the vote each party wins in each region. For a more thorough discussion of mixed member proportional check out the first two posts in this series (here and here). In my simulations*, I break the province into two rural regions, Vancouver Island (outside of Victoria) and the Interior. I worry that making the Interior a single region is problematic because of the differences between the North of the province and the South. At the same time, I worry that breaking the province down into smaller regions will produce results that are highly disproportional. In small regions there will not be enough list seats available to compensate for the disproportionality in the riding seats awarded on a first past the post basis.
I run simulations based on vote totals from the 2017, 2013 and 2009 provincial elections. It is important to note here that voters will vote differently and different parties will run under different electoral systems. These simulations are meant to illustrate proportionality at the province-wide and regional levels, not to predict what would have happened in previous elections had they been run under a different electoral system. I have a particularly low level of confidence in my predictions regarding the results of the STV urban ridings. Without second or third choice votes, it is impossible to know with any certainty how many seats each party would have won in each riding. I make estimates by calculating the threshold in each new STV district. I then subtract the threshold multiplied by a multiplier for a certain number seats (I start with 0, then 1, then 2, and so on) from the parties share of the vote to estimate the vote share for each of the parties’ candidates. The first candidate from a party gets the vote share for the party in the region, the second candidate gets the vote share minus the threshold, the third candidate gets the vote share minus the threshold x 2, and so on. I award seats to the candidates with the most votes until all seats are filled. It is important to note that this produces a rough estimate and is not actually reflective of how seats are assigned under STV.
The graph below shows that this system produces results that are the most part reasonably proportional, but that do vary in their proportionality. The Liberals are very proportionally represented in 2009, while the NDP’s seat share in 2017 is quite close to their vote share. The system can also produce some disproportionate results, though. The NDP ends up over-represented by 5 points 2013, while the Liberals are over-represented by 5 points in 2017. This disproportionality can have some significant effects on elections results. In 2013 the Liberals get close to a majority on 44% of the vote. In 2017 the system takes a vote difference between the NDP and Liberals that is within a point and gives the Liberal a 6-point edge in seats over the NDP. In each election I simulate the Greens end up under-represented, but never by very much.
The three graphs below show that the system produces quite proportional within-region results. Like in every system, the Liberals are consistently over-represented in the Interior relative to their vote share. The 2017 results on Island are really close to their vote share, but there are gaps in most other regions in most other years. Most notably, the Liberals end up under-represented in Vancouver/Burnaby in 2017 by around 8 points.
The cause of this variation in representation in each region is the low number of list seats and seats in STV ridings. The fewer the seats in an STV riding, the less proportional the result. There are only so many ways you can split 4, 5 or 6 seats amongst parties. Such systems can distinguish between 20 percentage point differences in the vote, but they struggle to accurately reflect differences of 5 or 10 points. The same problem exists with the limited number of list seats in rural districts. The fewer the list seats, the harder it is to balance out any disproportionality in the first past the post seats awarded in MMP. The result is the potential for significant disproportionality within regions.
It is possible for this disproportionality to add up to a quite significant province-wide disproportionality. There is nothing stopping a party from being slightly disproportionately over or under-represented in each region. This in turn would lead to significant over or under-representation in the province as a whole. For the most part in the simulations the regional disproportionalities cancel each other, but there is no reason that they should have to. When they do not, the somewhat problematic results noted in my discussion of overall provincial proportionality occur.
The graph below shows regional breakdown of party caucuses based on the 2017 results. The NDP and Greens are quite well represented, with NDP caucus mirroring the regional disproportion of their vote share very closely. The Greens are over-represented by a bit in Vancouver Island and on the Lower Mainland and under-represented in Vancouver/Burnaby, but in neither case is the difference that large. The Liberals face the problem they face in every simulation I have run. They are over-represented in the Interior, and under-represented on Vancouver Island and in Vancouver/Burnaby.
Rural urban proportional does regional representation reasonably well, but also has cases where parties’ regional representation do not match their vote share. It does province-wide proportionality less well. In some cases, it gets parties’ seat shares quite close to their vote share, in other cases it can be off by as much as 5 percentage points. The system is quite complex, not just in the way that it counts votes but also in what it requires of voters. Voters in STV districts need to learn about multiple candidates from multiple parties. They also have to understand the strategic implications of ranking candidates from the same party together or splitting them up. On top of all of this, voters moving from rural BC to urban BC (or vice-versa) would have to learn a new electoral system. The complexity coupled with the potential disproportionality of the system likely make it inferior to the two other proportional options being put to the referendum.
*Like with the boundaries for ridings under STV, how the rural parts of the province would be divided into regions would be decided by a boundaries commission after the system is adopted.