March 14, 2009

Non-Monotonicity and BC-STV

What do you think of a voting system where you can win by encouraging some of your supporters not to vote for you? That's one of the fundamental flaws with BC-STV.

Supporters of BC-STV like to say that it insults the intelligence of B.C. voters to say that the system is complex. Tell that to the mathematicians who investigated what's called the "non-monotonicity" of STV.

Monotonicity means not decreasing as support increases, or not increasing as support decreases. Mathematicians have demonstrated that STV is non-monotonic. Proponents of STV claim it has not spread because evil politicians are out to kill it. In reality, rational people have rejected it because it is a fundamentally flawed system where the winners can change with random changes in rankings or a shuffling of the ballots in a recount. The counting system is so complex that it is virtually impossible to take actual vote counts and analyze how vulnerable they are to changes in outcome due to improvements in rankings. Those who understand the system know that election campaigns can be focused so as to exploit the counting weakness.

Most British Columbians are probably more inclined to reject BC-STV because of its outrageous elimination of local representation in favour of regional representation, rather than because the vote count is non-monotonic.

Under BC-STV Kamloops would be part of Cariboo-Thompson, an enormous 5-MLA electoral area reaching from Quesnel to the U.S. border, an area of 141,000 sq. km. - twice the size of Ireland; voters would have one vote to elect 5 MLAs for the region. Voters in Quesnel would be in the same electoral area as voters in Penticton. Voters in Tofino would be in the same electoral area as voters in Powell River. Voters in the West End would be in the same electoral area as voters in Kerrisdale.

Looking at the map and seeing what BC-STV would do to communities, is likely to turn many British Columbians against BC-STV. Those who prefer mathematics over maps will reject it because its counting system is fundamentally flawed.