STV in 2 Dimensions

Here are 14 scatter charts from PoliticalSim TM. They show simulated voters as small dots and candidates as big ones. Losers get X and winners get halos.   Simulated voters rank the candidates, giving 1st choice to the closest, 2nd choice to the 2nd closest, and so on. Their locations may represent geography or political positions. But the STV rule allows an unlimited number of issues -- voters decide what is important.   A simple web page can show only 2 dimensions: left-right, and top-bottom.   A voter's dot has the same color and shape as his current top preference - the closest candidate. A voter's dot disappears as his vote (or "weight") is used to elect his rep(s). The numbers show each candidate's percentage of the votes.   The 13 candidates and 241 voters condense into 5 reps in 14 steps.   The voters below are arranged in a checkerboard. This simple pattern makes it easy to see transfers. (PoliticalSim is used more often to create uniform, random, and normal distributions. Players move their candidates, seeking the best positions for whichever voting rule is in play.)   Single Transferable Vote, Simple Quota, 5 Seats   Steps 1 through 6. No one wins a quota of ballots so the candidate with the fewest ballots is eliminated.

Steps 3 and 4.

Steps 5 and 6.

Steps 7 and 8. One candidate reaches quota and is elected. Supporters have spent their weight.

Steps 9 and 10. The second winner has more than enough votes.
A share of the excess transfers to each supporter's next choice.
Voters with weight 0.1 show as small red dots in the lower left.
One voter on the far left preferred the yellow square.

Steps 11 and 12. The green diamond loses; the blue diamond next to it wins.

Steps 13 and 14. The last two candidates get elected.

 

In this case STV elected a candidate close to the center but not the candidate closest to the center.  More importantly, the most central STV winner needs intense support and high ranks from central voters only -- she does not need to seek the support of moderate and fringe voters.  There is no one on this STV council primarily interested in broad policies.  The ensemble councils explained next can do better.

Accurate Democracy
Electoral Systems			Legislative Systems
Chair	Representatives Merits of PR Electing women Quotes STV Picture tally 1,   2   2D charts doc Ballot Anti PR Options	Council	Policy	Projects by STV	Budgets