Jamaica 2011: As good as PR–or not (updated)

Final results show the PNP won with 53.3% of the votes, to the JLP’s 46.6%. However, even as the final vote total was much closer than the preliminary result upon which this entry was based, the PNP picked up an additional seat. (Note that this gives it exactly two thirds of the seats.)

Thus the result was far from proportional, after all. In fact, it was even more majoritarian than a “typical” FPTP result would be with the given input parameters. The PNP’s Advantage Ratio is 1.25, whereas the Seat-Vote Equation would predict it to have been 1.14.

I am leaving the rest of this as originally crafted. The analysis of other elections stands, but that of 2011 would be altered by this new information. Thanks to Jon, in a comment, for the tip.
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Jamaica held its general election on 29 December. Like the other former British territories in the Caribbean, Jamaica elects its parliament by first past the post (plurality) in single-seat districts. Also like other English-speaking Caribbean islands, Jamaica has a parliament that is significantly undersized, given its population. So this makes Jamaica a perfect opportunity to break out our old favorites, the Cube Root Rule of Assembly Size, and the Seat-Vote Equation.

The election result itself saw an alternation in power from the Jamaican Labour Party (JLP) to the Peoples National Party (PNP). Various news reports before the election had said the election was expected to be close. But it was not. The PNP won 41 seats to the JLP’s 22. Thus the JLP was defeated after a single term, which had been its first time in power since its defeat in 1989. (That was a two-term government, although its second term then was tainted by the PNP’s election boycott in 1983.)

The Jamaican case is of some interest to comparative elections specialists because it has an almost perfect two-party system. The two main parties combined for 99.87% of the vote in this election. The PNP won 61.3%.

Only once since 1959 has the third party in a Jamaican election won more than 1% of the vote (NDM, 5.2%, 1997). That makes Jamaica arguably a more “pure” two-party system than its very large neighbor to the north, and probably the biggest country to have a strict two-party system other than that really big one.

So, how did the system perform, in terms of the proportionality of translating votes into seats? We might expect a party winning over 60% of the vote in a first-past-the-post system to be significantly over-represented. The expectation is all the greater given the small size of the parliament, for the country’s population. With a population of around 2.7 million (just over a million voters), the Cube Root Rule would lead us to expect an assembly of more than double its actual size of 63. ((To be fair, they did increase their assembly size. It was only 60 seats from 1976 to 2007!)) Smaller assemblies mean less proportionality, other things constant. They tend to produce very high disproportionality under FPTP.

Yet the PNP’s 41 seats represent 65.1% of the total, hardly at all greater than its 61.3% of the vote.

The Seat-Vote Equation suggests that a “normal” case of about one million voters, 63 seats, and the top two parties at 61% and 38% of the votes would result in a leading party winning 84% of the seats. That would have been 53 seats, to 10 for the JLP.

In the 2011 election, then, Jamaica’s electoral system produced an almost completely proportional result.

This is not a systemic tendency, or if it is, it is a very new one. In fact, the Advantage Ratio (percent votes divided by percent seats) for the largest party in Jamaica had never been below 1.10 before this election (when it dropped to 1.06). Something has been going on in Jamaican elections recently: Every election that was contested by both major parties since 1959 had seen an Advantage Ratio of at least 1.16. Every contested election from 1976 through 1997 saw this ratio be at least 1.33, peaking at 1.50 in 1997, when the PNP won a third consecutive term. Then suddenly it dropped to 1.12 in 2002, when the PNP won a fourth term, in a very close election (50.14% to 49.77%). ((And, in case you are wondering, as I was, I checked: there is only a small relationship in FPTP systems between the top two parties’ difference in votes and the largest party’s advantage ratio. The effect is statistically significant, but the coefficient is around only .007. In any case, the falling ratio in close elections in 2002 and 2007 is consistent with the modeled relationship, but the greater fall in 2011 is most certainly not.))

From looking at the data on seat allocation, I can’t tell what has changed. But I can certainly tell that something has. For the third time in a row, the result has been unusually proportional for a FPTP system–and, in 2011, quite proportional for any electoral system.

The election was called early, as one was not due until the fall of 2012. The Prime Minister, Andrew Holness, in September replaced Bruce Golding (yes, another case of inter-electoral change of PM through “intra-party” mechanisms). Apparently, Holness felt he needed to go to the people for a new mandate. Apparently, it did not work out so well.

As an aside, how often do countries (especially in the Western world) hold elections in the final week of December? I imagine it must be very unusual.

As a further aside, in how many other countries is the more right-wing of the major parties called “Labour”? Or does the more left-wing party have “National” in its name? ((Yes, of course, it also has “People’s”, which is pretty much the only way I can remember which is which.))

Data cited in this entry are from my own research files.