Monday, February 15, 2016

Best Methods for Electing a Group of People

In our previous post, we provided our recommendations for the best voting methods to use when electing a single person.  In this follow-up post, we give our recommendations for electing a group of people.

Proportional or Majoritarian Representation?

The first thing to decide is whether you want proportional representation or majoritarian representation.  Proportional representation means, in a nutshell, that the demographics of the elected group should be similar to the demographics of the voters.  For example, under proportional representation, 50% of elected bodies would be women and parties and ethnic minorities would be represented according to their support among voters.

Majoritarian representation means that the majority group should be able control every single available seat.  In the future, we'll do another post with more details of when you might want to consider majoritarian representation.

To give an example, suppose you live in a city that elects a city council of 10 people each year, and that about 60% of the voters favor Democrats and 40% of the voters favor Republicans.  If you think the fair outcome is that 6 of the 10 council members are Democrats and 4 of the 10 council members are Republicans, then you want to have proportional representation.  If you think the fair outcome is that all 10 council members are Democrats, then you want majoritarian representation.

If your organization is electing a group, such as a committee or council, then you want to have proportional representation so that you can represent the views of all of your members.

For most organizations, the best way to obtain proportional representation is to use a version of the single transferable vote.  Other voting methods, such as list voting or MMP, are possible but generally not practical outside of government elections.

Single Transferable Vote (STV)

Similar to instant runoff voting, STV methods also eliminate losing candidates and transfer their votes to other candidates.  The interesting part about STV is that there is a second kind of transfer!  Candidate with too many votes also transfer some of their votes to other candidates.

Too many votes?!?  How can a candidate have too many votes?  We'll use an example to explain.

Suppose a city is electing 3 councillors, the city is highly partisan, 90% of the voters favor Republicans, and 10% of the voters favor  Democrats.  Further suppose that the Republicans have 3 candidates (named R1, R2, and R3) and the Democrats have two candidates (named D1 and D2).  The following is a possible outcome of first choices:

85%  3%  2%  5%  5%

Although Republicans make up 90% of the electorate, we have a situation where two of the three seats go to Democrats.  How could this happen?  Because R1 got too many votes!

Here is what might happen if we transferred some of R1's extra votes:

25%  24%  25%  14%  12%

Presumably, most of the people who voted for R1 would prefer other Republicans over the Democrats, and when R1's extra votes are transferred, most of them go R2 or R3.  Now that R1's votes have been transferred, the Republicans will win at least two seats, which makes for a more proportional outcome.

The above example isn't that realistic, but it does show how a voter can have too many votes and why transferring extra votes can make the outcome more proportional.  Watch the video linked at the top of this page to see a cool example of an STV count.

All STV counting rules follow these principles, and we'll next give you our recommendations.

Scottish STV

Because we value simplicity and understanding of how the voting process works, our top recommendation to most organizations is to use Scottish STV.  The two main advantages of Scottish STV are (i) the rules are reasonably easy to understand and apply, and (ii) the rules are very well defined in Scottish law! We have a separate blog post explaining how votes are counted with Scottish STV.

If your organization wants to use Scottish STV, you can simply state that in your by laws (no need to describe the counting process in your by laws because it is already defined) and then use OpaVote to count the votes.

Meek STV

For organizations that are comfortable with more complex counting procedures (e.g., mathematicians and computer programmers), we recommend Meek STV.  Meek STV provides better proportionality than Scottish STV, but it takes more effort to understand how it works. We have a separate blog post explaining how votes are counted with Meek STV.

If you are mathematically inclined and curious about voting, I strongly recommend reading about Meek STV.  How it works is really cool!


Lastly, I'll mention the ERS97 STV rules.  I start this section with the adverbial enumerator as a nod to our friends across the pond who created these rules.  The Electoral Reform Society in the UK has long been a staunch advocate of STV and their suggested rules are commonly called ERS97 (because they were finalized in 1997 and to distinguish their older rules finalized in 1976, 1973, and 1955!)

The ERS97 STV rules are used by quite a few organizations in the UK.  The rules were designed to facilitate hand counting of a large number of ballots.  In our view, they are not needed today since ballots are counted by computers.  The rules are somewhat complicated and don't provide any better results than the Scottish rules, so we favor the Scottish rules.