The final lower house results from the South Australian election have now been decided, giving Labor 26 seats, a net loss of only two despite a drop in its vote of 7.8%. Final results from Tasmania aren’t expected until tomorrow or Thursday, but we can already summarise the key difference between the two: Tasmanians will substantially get what they voted for; South Australians didn’t.

Here are the percentages of votes and seats won in South Australia:

PARTY % VOTES % SEATS
Liberal 41.7 38.3
Labor 37.5 55.3
Greens 8.1 0
Family First 5.4 0
Others 7.3 6.4

Now here are the corresponding figures for Tasmania (assuming the Liberals win the last seat in Denison):

PARTY % VOTES % SEATS
Liberal 39.0 40.0
Labor 36.9 40.0
Greens 21.6 20.0
Others 2.4 0

Notice the difference?

I’ve said before that designing a fair electoral system isn’t rocket science, and here’s the proof — same day, same country. One state gets a parliament where each party’s representation corresponds approximately to its support. The other fails miserably.

Nor is it the distribution of preferences in South Australia that’s making the difference. After preferences, 51.6% of South Australians voted for a Liberal government. But they didn’t get it. On what possible understanding of fairness can that be described as fair?

If South Australia had the same voting system as Tasmania, with five-member electorates and proportional representation, the result would have been something like: Liberals 22, ALP 18, Greens 4 and one independent. (It changes a bit depending on boundaries and assumptions about preferences, but that’s a good approximation.) Still not perfect, but a much better fit to what people actually voted for.

Interestingly enough, if you reverse the experiment and imagine Tasmania voting as single-member electorates, the result doesn’t change very much: I tried it and got 12 Liberal, 10 ALP and three Greens (although of course that’s even more sensitive to just where you draw the boundaries). The Greens are still disadvantaged, but in Tasmania their vote is now large enough to guarantee some representation regardless of the system.

In a less even result, however, the unfairness would be more obvious: after the 2002 Tasmanian election the same exercise produced a parliament with 23 ALP, two Greens and no Liberals at all.

It’s long past time that Australia had a serious debate about this issue. In the past, single-member electorates usually worked against the ALP; as recently as 1998 it lost a federal election despite having majority support from the voters. Now, as in South Australia, it’s usually the coalition that misses out: in Victoria, New South Wales and Queensland the Opposition will probably need 52% of the vote or more in order to win government.

Meanwhile, minor parties are routinely deprived of the representation that their votes deserve — unless, like the National Party, their support is highly concentrated, in which case they can be ridiculously over-represented.

Tasmania’s system isn’t perfect, but it’s streets ahead of other states when it comes to fairness. The rest of the country should be watching and learning.