How Japan’s proportional representation voting system works, from Nikkei

Today’s Nikkei print edition has a great Q&A about Japan’s proportional representation system. Here is my explanation for how it works, borrowing from that Q&A and some Internet sources:

  • There are 180 seats (of the lower house’s 480) that are decided by PR. The country is divided into 11 regions, or “blocks”, which each receive some of the 180 seats. In addition to voting for a candidate in their single-member district, voters write in the name of the party they wish to receive their region’s PR seats. Votes remain valid if they are for an individual running on that party’s PR list, or if they are for the party leader.

  • Seats are awarded using the D’Hondt method. Though somewhat complicated, this is a fair system for allotting the seats as intended. Putting it in my own words would be tough, so I’ll just quote Wikipedia:

In a closed list system, each voter casts a single vote for the party of their choice. In an open list system (such as Japan’s), the voter votes for a candidate personally, but the vote is principally counted as a vote for the candidate’s party.

After all the votes have been tallied, successive quotients or ‘averages’ are calculated for each list. The formula for the quotient is textstylefrac{V}{s+1}, where:

  • V is the total number of votes that list received; and

  • s is the number of seats that party has been allocated so far (initially 0 for all parties in a list only ballot…)

Whichever list has the highest quotient or average gets the next seat allocated, and their quotient is recalculated given their new seat total. The process is repeated until all seats have been allocated.


If you don’t want to go through the calculation, you can use the following shorthand for your region – for example, for a party to win one of Tokyo’s 17 PR seats, it needs to garner 1/17 of the vote, or 5.9%. Every 5.9% of the vote after that gets it another seat. It’s not precise but it’s a rough indicator.

  • Parties are required to submit a list of PR candidates in advance, with candidates prioritized by region. For example, the LDP’s list prioritizes incumbents, many of whom are also running in single-member districts (see below).

  • Candidates are allowed to run both in a single-member district and one PR block. This means if the candidate loses in the single-member district, he or she can still be sent to the Diet if the party wins in the PR block.

  • It is possible to give two or more candidates the same level of priority if they are running in single-member districts (they then act like understudies for each other). A double-candidate who wins in the single-member district is automatically withdrawn from the PR list and the understudy takes his or her place. Note that in the LDP’s list, the first 22 candidates are all tied for first in priority. If only one wins in the PR block, then all 22 will get seats before the 23rd candidate.

  • PR candidates who were given equivalent priority who lose in the single-member districts are not given sub-ranks ahead of time. The seats will be alotted among them in order of who came closest to winning in their respective single-member districts. So if Yukari Sato loses in Tokyo’s 5th district by just 1,000 votes and Yuriko Koike loses in Tokyo’s 10th by 2,000 votes, then Sato would be given priority over Koike.

  • If a party wins in an unexpected landslide, there is a possibility they could fail to field enough PR candidates to satisfy the voters’ mandate. In that case, it sucks to be them because the seats go to the party who got the next greatest number of votes. This happened in 2005 when every candidate won on the LDP’s PR list in the South Kanto block, resulting in the election of 25-year-old Taizo Sugimura. They had enough votes to get at least one more seat but had to give it up to another party (story courtesy of Lord Curzon). This strikes me as a little undemocratic, since that means a party that the voters specifically voted against will win a seat.

14 thoughts on “How Japan’s proportional representation voting system works, from Nikkei

  1. Don’t forget, if a candidate is running in both a single-member district and a PR block, they need to garner at least 10% of the vote in their single-member district in order to be elected by PR.

  2. What is significance of the number 22? Both LDP and DPJ gave the top 22 PR candidates equal priority.

  3. As far as I can tell it’s a coincidence. The Tokyo region has 17 seats, so at some point giving a lot of people “top” priority would lose its meeting and end in a lot of hurt feelings.

    The Wiki article on the dual candidacy phenomenon makes no mention of a limit.

    http://ja.wikipedia.org/wiki/%E9%87%8D%E8%A4%87%E7%AB%8B%E5%80%99%E8%A3%9C%E5%88%B6%E5%BA%A6

    The election law doesn’t explicitly write out all the details of the PR system and I can’t seem to find where those detailed rules are written down…

  4. “If a party wins in an unexpected landslide, there is a possibility they could fail to field enough PR candidates to satisfy the voters’ mandate.”
    That just happened again, the DPJ won more seats than it could fill.

    “This strikes me as a little undemocratic, since that means a party that the voters specifically voted against will win a seat.”
    The whole PR idea strikes me as undemocratic. I recently read a quote from a woman who was a JCP supporter but lived in a district where the JCP did not have a candidate for direct election. So she said she’d vote for the DPJ’s candidate and the JCP.

    Enough people like that in such an area and the JCP could get a PR seat for that block even if they ran candidates in other areas of the block and all of them lost their respective elections.

    The DPJ has said they would cut most of the PR seats, here’s hoping they mean it, or better yet just cut all of them and go to a strict first-past-the-post system.

  5. If PR seats are cut then Komeito and Communists are dead in the water (LDP would have been even more badly beaten last night as well)

    I think PR seats are important for Japan because of its very wide political spectrum. With PR you can keep excessive swings one way or the other in check and also ensure that a broader range of voices are heard.

  6. I have to disagree, Adamu – you force more swings having PR as it gives fringe parties a pull all out of proportion to their actual popular mandate. Look at what has been going on in the upper house, where DPJ needed (needs? although with a majority in the lower house the need to worry about the upper house is not such an issue…) to keep the SDP and other happily in a coalition arrangement, and thus had to either temper what the DPJ wanted to do or outright pander to a couple of batty obasans and ojisans.

    If parties like the SDP and JCP want to win seats then they need to do so on the merits of their platform. The vast majority of voters clearly do not want them in power, and votes for those parties have long been negative votes against the LDP, not positive votes for something. Ironically, by splitting the opposition votes the SDP, JCP and other fringe parties were just prolonging LDP rule. I recall a couple of elections where the LDP “won” with a minority simply because the 60% of voters who were against the LDP couldn’t agree to support the only opposition party who could otherwise have reasonably been expected to beat the LDP. Which is why I’ve long said that a vote for the SDP or JCP is a vote for the LDP.

    Eliminate PR seats – if those consolation seats are the only way Komeito, the JCP or any other party can “get a voice”, then they need to figure out a new plan and speak with a voice people actually want to hear and that will get them elected. Otherwise they are nothing but an irrelevant distraction that keeps the people who voters DO want in office jumping through hoops.

  7. I’ve lived in Japan long enough to see the other options with their respective faults and merits. The multi-seat district system was much kinder to small parties; the new system has actually just about killed off the socialists and a whole bunch of other groups have disappeared altogether. But the new system has also made possible huge swings like we have seen in the last two elections, and I’m not sure this is altogether a good thing from the standpoint of checks and balances. What LB proposes would make for even larger swings.
    In the old system, it was possible to vote for a party you actually believed in. Today, we mostly have to hold our nose and vote for the lesser of evils. But the old system also gave voice to the communists and socialists and other groups. I don’t see the merit of shutting their voices down entirely.

  8. LB, your argument doesn’t make sense. If anything, PR gives fringe parties a pull more proportional to their popular mandate. Millions of Soka Gakkai people vote for Komeito, but they don’t have enough of a plurality anywhere to get a candidate through a “first past the post” vote. PR at least ensures them a few seats at the table. It doesn’t give them a disproportional pull unless neither big party/coalition can reach a majority, but then again, their pull is still not that disproportional since they have to reach a consensus with the remainder of a majority.

    Anyway, here’s another creative use of split voting: One friend of mine lives in a district (Tokyo 1) where she likes the LDP candidate (Yosano) and hates the DPJ candidate (Kaieda), but she didn’t want to register approval of the LDP in general, so she split her ticket Yosano/DPJ. Didn’t do her much good since they both got voted in anyway.

  9. @wataru – True, PR seats give a voice to parties like the JCP, SDP and YP. But to what end? OK, YP is brand-spanking new, but from the historical record it is pretty easy to guess what they will accomplish as a party of 5: nothing. Not a G-D thing. So the value of their “voice” is… Someone? Anyone? Bueller??

    Well unless, as I already said, you were an LDP candidate, in which case “giving them a voice” translated pretty directly into “keeping you in office”. Yes, having those fringe parties around prevented huge swings from taking place at election time – because they prevented any swing from taking place at all and allowed the stagnant core to rot away do the detriment of the country as a whole while vanity parties kept scampering around the edges accomplishing nothing.

    And that is exactly what parties like the JCP and SDP are (or were, prior to the last upper house election) – vanity parties. Did they have any meaningful impact in the political arena in terms of legislation passed or deeds accomplished? And I mean aside from the SDP getting Arimoto Keiko and Ishioka Toru murdered by informing North Korea that they had smuggled a letter out.

    @Joe – your third sentence is exactly what I was talking about. The DPJ could not clear 50% in the upper house on its own, and so was entirely reliant on the SDP and PNP in particular to control the house. They are still reliant on those parties as they do not have a 2/3 majority on their own in the lower house to over-ride an upper house veto. So if they decide to do something which their coalition “partners” (coalition remoras might be a more apt description) don’t like, they can get it through the lower house once, have it rejected by the upper house and then be stuck trying to round up enough votes to over come the dissent of 2-3 people who really have no good reason to be wearing a Diet member’s badge anyway. The DPJ may have the greatest numbers, but unless they are able to lure a few more people across the aisle to stand firmly on their side the SDP has a hand on the wheel.

    As for the Komeito supporters, well my heart bleeds. Lots more people out there voted for the LDP only to see their candidate lose flat out, both in local seats and PR seats. What of them? Won’t someone think of the (Koizumi) children? Everyone gets a voice in the form of a ballot – not everyone gets their voice heard. Majority rules. Again, as I said above, if Komeito wants to be in the business of governing the country then they need to come up with a platform that the majority of the voting public in a given district can support, and present a candidate that that same majority will get behind and vote for, regardless of whether or not those voters think Ikeda Daisaku is the greatest thing since sliced bread or not. If they can’t do that then they have no business being in office.

  10. Well, I can’t argue with the philosophical statement that “a party which doesn’t get the most votes shouldn’t count for anything,” which is a value judgment ultimately no more incorrect than “a party which gets a significant number of votes should count for something at some point.”

    The thing is, I come from a country where winner-take-all is absolutely the case—i.e., the United States—and we ended up with a government where third parties not only have no hope of winning, but often end up helping diametrically opposed parties. For twelve years, we had presidents elected without the mandate of the majority, simply because they were “first past the post” in the largest number of districts and had a third party candidate siphoning votes from their opponent. We really ended up ruled by minorities for those 12 years. This is what happens when you follow a purely winner-take-all system.

    My favorite voting system is the disappointingly rare single transferable vote employed in Ireland and Australia, where voters rank candidates and their lesser choices can be counted to reach a final selection. It can be used in either a single-seat or PR voting bloc environment, though I can’t personally decide which makes more sense from a democratic perspective.

  11. Joe, I am originally from the US too. And the name “Nader” kept running through my head as I wrote the above. I see what you are saying, but Japan has been in effectively the same boat for years. I still recall my first election here where I actually understood some of what was happening, and being absolutely gobstruck by the fact that the LDP could win an election with under 40% of the votes cast. We’re not even talking third-party candidates at this point, it is 3rd, 4th, 5th and 6th party candidates, none of who would cast their votes to the other guys and none of whom would do anything to help the “2nd party”, which was the only one which could have toppled the LDP. This has been going on for as long as I have been here, and each time I watch parties like the JCP and SDP clinging on by their fingernails as they just squeek in on PR ballots and deny just enough of the vote to the one big opposition party so that the LDP wins again. Each time I find myself screaming at the TV: “What hippie dinosaur voted Communist AGAIN? Give it up already and stop being an enabler for the LDP!”

    Sure, perhaps having only two parties means “voting for the lesser of two evils”. But I will gladly take that over having one evil win all the time because everyone who is against them is dickering over which of the other guys is an “acceptable” evil.

  12. Hey, LB, we now have the lesser of two evils plus a few smaller parties to keep them in check on certain specific issues. I was happy to vote for Kan Naoto and also to vote for the socialist party, hoping it will help influence the DPJ on issues I care about.
    Under the old system, the socialists were vital to keep the LDP from swinging too far to the right. They are much smaller now, of course, under the new system, but can still play a role, I believe.

  13. I don’t have a long history with it, but my father, who voted for John B. Anderson and other independent candidates, gnashes his teeth and tears his robe whenever he sees evidence that the ass and the elephant are colluding to keep the third party out. I’ve heard of state police, at the behest of a certain late Senator of quasi-royalty status, physically barring Ralph Nader from entering a political debate that he had every right of joining. And it’s my understanding that this kind of combining of special interests has happened consistently since the days of Ross Perot.

    Sure, it makes it easier for the country to decide its election by duking it out, blue vs. red, but it doesn’t ensure that everyone is represented. As for Japan, I don’t vote, but judging by what I’ve seen I don’t see how under-representing minority parties (whether you consider them vanity parties or not) makes anything any better. From an entertainment perspective, we need these smaller parties to kick up a stink whenever politicians from the larger parties get themselves into trouble.

  14. We also need police and prosecutors who will go after gangsters and uyoku dantai, but I’m afraid that would be too democratic for this country. Where’s our Japanese version of Rudy Giuliani?

Comments are closed.