How does the Single Transferable Vote compare with the current system? Let's look at how the 2005 provincial election might have gone.
2005 Election Results with 2009 Boundaries
In 2005 the Liberal party received 46% of the popular vote and won 58% of the seats in the legislature. If we remap the polling stations into the proposed 2009 electoral districts, the Liberal party would still receive 46% of the popular vote and would win 54% of the seats.
See Detailed Results See Original 2005 Results
2005 Election Under BC-STV
If BC-STV had been in effect in 2005, this is what might have happened. The Liberal party would have won 41 of the 81* seats, or 51%. This is closer to the 46% of the popular vote, though it is still not completely proportional.
*Note: the district boundaries were re-adjusted after I completed this website, and the number of seats changed from 81 to 85. I have not had time to re-create the maps for this website — please see the BC-EBC website for the most current boundaries.
Assumptions
Running the 2005 provincial election under BC-STV requires a number of assumptions:
- I took the results from the polling stations used in 2005 and remapped them into the proposed 2009 electoral districts.
- To get the remapped 2005 results, I assume that a voter who chose a Liberal candidate in one voting area would continue to choose the (new) Liberal candidate if the area was mapped to a new district, etc.
- To get the BC-STV results I assume that voters vote along party lines. If a ballot was cast for the Liberal party under the old system I assume that under BC-STV the voter would list all Liberal candidates in the order they appear on the ballot.
If voters do NOT list candidates in order (i.e., if they vote for the actual candidate they chose in 2005, then transfer the ballot to other candidates in the same party) the election comes out differently — the seats won are 53%, 43%, and 4%. I consider this to be unlikely since I suspect that most people will be entering the polling booth with a list of parties in mind rather than a list of candidates.
Taking it Farther
One feature of BC-STV is that you can list candidates from more than one party. If I assume that voters take advantage of this to spread their votes around to similar parties, we get slightly different election results:
Election Results with Cross-Party Voting
The above election results come from making some new assumptions:
- I assume that voters who chose a strongly conservative candidate in 2005 (i.e., Reform) would first list that party, then list other strongly conservative parties (i.e., Unity, BC Conservative), and then list the Liberal party (the likely conservative victor).
- I assume that voters who chose a strongly left-wing candidate in 2005 (i.e., Communist Party) would first list that party, then list other strongly left-wing parties (i.e., People's Front), then list the NDP (the most likely left-wing victor).
- I assume that voters who chose a progressive candidate in 2005 (i.e., Marijuana Party) would first list that party, then list other progressive parties, then list the Green party (the most likely progressive victor).
As you can see, even with these extreme assumptions, the election results turn out quite similar to BC-STV without cross-party voting. The liberals edge into a majority victory because of the large number of extreme right-wing parties, whose voters are now transfering their votes to the Liberal party.
Even Farther
What if we make an extreme assumptions? What it it is a "Liberals vs. NDP" election?
- Nobody who votes Independent lists other options.
- Everybody who votes for a conservative party lists the Liberals as their last choice.
- Everybody who votes for a left-wing or progressive party lists the NDP as their last choice.
Election Results with "Liberal vs. NDP"
In this extreme case we can see that the use of BC-STV leads to a different government — we go from a Liberal majority to an NDP minority government.