Consider an electorate divided solely on some linear issue X. Assume the breakdown is as follows:
| Wants more X | Wants same X | Wants less X |
|---|
| 45% | 20% | 35% |
Assume also that each position has only two representatives. Pretend you’re a voting system and imagine the ballots these people submit to you. How do you aggregate these votes to best represent the electorate? I’d argue the following is fair:
| More | Same | Less |
|---|
| 1 winner | | 1 winner | |
|---|
| 2 winners | 1 winner | | 1 winner |
|---|
| 3 winners | 1 winner | 1 winner | 1 winner |
|---|
| 4 winners | 2 winners | 1 winner | 1 winner |
|---|
| 5 winners | 2 winners | 1 winner | 2 winners |
|---|
| 6 winners | 2 winners | 2 winners | 2 winners |
|---|
As an aside, note that the result at 6 winners isn’t really proportional to the popular vote, but that we were constrained by the number of running candidates. Had More X another candidate to run, More/More/More/Same/Less/Less would have been a fairer result.
More to the point though, notice the oscillation between the 1 and 2 winner scenarios. Although the electorate is best represented with a single Same X winner, More/Less better represents the electorate than Same/Same. While this holds true when the number of winners is known and fixed, our notion of fair changes when the number of winners is variable.
Consider the scenario where you have one representative, but occasionally need a second. Since the first representative is fixed, you choose your second proportional to the electorate. We’re looking at generating an ordered list of candidates.
| Proportional Ranking |
|---|
| First place | Same |
|---|
| Second place | More |
|---|
| Third place | Less |
|---|
| Fourth place | More |
|---|
| Fifth place | Less |
|---|
| Sixth place | Same |
|---|
Note the difference here between a fixed two-winner election (where we chose More/Less) and the proportional ranking (which starts off Same/More). In this different problem space, a fair outcome produces different results.
Lastly, consider the scenario where you only need one winner, but you need a runner up in case the first winner is unable to take the position.
| Non-proportional Ranking |
|---|
| First place | Same |
|---|
| Second place | Same |
|---|
| Third place | More |
|---|
| Fourth place | More |
|---|
| Fifth place | Less |
|---|
| Sixth place | Less |
|---|
Where in the first example we provided More/Less as a fairer alternative to Same/Same, the problem space for this third example would dictate Same/Same over More/Less. Again, different results for the same notion of fair.
These three scenarios have produced significantly different results, illustrating fixed-winner allocation, proportional ranking and non-proportional ranking. Hopefully this highlights the need to determine in advance the context in which you’re bringing things to a vote.
The one question I have in all of this is how to distinguish between these two problems:
- One winner every couple of years (e.g. federal elections) is likely best suited with fixed-winner allocation
- One winner every hour (e.g. a board game marathon) is likely best suited with proportional ranking
Is the salient difference here that preferences can change over time? That the voters themselves change over time? Or is it that you can opt to take a break during the next board game if you don’t like it, but you can’t quite opt out of being a citizen (at least, not with as much ease). I’m really not sure here.