Tag Archives: assembly size

Japan: Assembly-size reduction fails, return to SNTV being discussed

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A proposal to reduce the size of the Japanese House of Representatives by 10% failed to pass in the autumn session. Meanwhile, there is discussion of reverting to Japan’s former electoral system of single non-transferable vote (SNTV). Via Japan Times, 2 January.

The assembly size reduction was part of the coalition agreement between the Liberal Democratic Party (LDP) and the Japan Innovation Party (JIP) that was signed last year. As an earlier (26 October 2025) Japan Times article noted that “Small parties that rely on proportional representation seats are on high alert,” because the plan would remove about 50 party-list seats allocated by proportional representation in Japan’s current mixed-member majoritarian system.1 Yoshihiko Noda, leader of the main opposition Constitutional Democratic Party of Japan, has called for the cut to include a reduction of the number of single-seat districts. As Japan Times notes, this would complicate the electoral “coordination” of the LDP.

The recent (2 Jan.) article on possible electoral system change does not refer to any specific proposal to bring back SNTV, but indicates there is “growing debate in parliament” about doing so. The justification given is:

Advocates for scrapping the current model say a multiseat district system would better allow parliament to reflect a diverse range of views and spur more voter interest by helping to cut down on “dead votes,” or ballots cast for candidates who end up losing their single-seat district race.

This is a specious line of argument. If these were really the goals, there would be better ways to achieve them. The only advantage to SNTV is it is familiar, given its use to elect the House of Representatives for decades prior to the mid-90s. However, better ways to achieve the stated goals would be either to convert the mixed member system to the proportional (MMP) type, or adopt list PR. Given the importance of personal votes in the LDP, open-list PR would be a sensible choice. In fact, half of the House of Councillors is already elected by open-list PR.

It actually gets worse, in that the recent JT article indicates some of the proposals circulating around would be for the limited vote, not SNTV. For instance, allowing the voter to vote for two candidates in a three-seat district. SNTV is, of course, a special case of limited vote, in the sense of limiting the number of votes to not simply less than the number elected in the district (the district magnitude, or M), but all the way down to one. Both have the basic feature of being pure candidate-based systems where the top M candidates win, regardless of party affiliation. By contrast, open-list PR would first pool the candidates’ votes at the level of the party list, before determining how many seats each party would win.

The Democratic Party for the People (DPP) is said to believe the limited vote “would avoid a concentration of power in a single party and foster a multiparty system.” This is seriously misguided. Most voters could be expected to give their full allotment of votes to candidates of the same party, and thus the limited vote, giving multiple votes per voter, is more favorable to the largest party than SNTV is. (Basic electoral-system theory!)

Readers interested in a discussion of SNTV may want to consult the recent post that started off being about Kyrgyzstan’s adoption of such system, but morphed into a very interesting discussion in the comments about the place of SNTV in the family of electoral systems (and related topics).

Thanks to those who called the first-linked JT story to my attention–Yibo in another thread here and my colleague, Ellis Krauss.

  1. One of the articles says it would be a reduction of 25 constituency seats and 20 list seats. It is not clear which proposal actually was voted on. ↩︎

The output indicators for Italy 2022: Yes, MMM in a smaller assembly really mattered

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In the pre-election planting I pointed out how much more disproportional Italy’s electoral system would be, given the substantial reduction in assembly size. The current allocation rules and balance between single-seat districts and list-PR seats remained unchanged since 2018, but the assembly size was cut from 630 to 400. (Here I will be referring only to the Chamber of Deputies.) The system is mixed-member majoritarian (MMM).

Assuming I calculated things correctly–and I think I did, but the party vs. bloc calculations can be a little confusing, so caveats apply–here is how the change mattered.

I will report effective number of seat-winning parties (NS), effective number of vote-earning parties (NV), and deviation from proportionality (D2, the Gallagher index also known as the Least Squares Index). I will report both by individual party and by pre-electoral bloc. I believe that for an electoral system like this, the bloc figures are more meaningful, but here you have both and can decide which one works for your analytic purposes.

2018 Party2018 Bloc2022 Party2022 Bloc
NS4.322.905.582.40
NV5.103.366.623.44
D2 (%)3.985.027.3011.74

The change is pretty dramatic. Taking that last line first–disproportionality–we see an increase at the bloc level from around five percent to nearly twelve percent. The 2018 bloc-level figure is a level just below what we might see in a moderately proportional system like Estonia (5.3% in 2019) or Spain (5.37% in 2016) or Luxembourg (5.20% in 2013). The 2022 bloc-level figure is closer to what we might find with a majoritarian system, such as Canada (11.3% in 1988) or the UK (11.8% in 2019) or to take a “brotherly” MMM example, Japan (11.5% in 2000). Thus the increase is quite consistent with how I characterized the system in the previous post, as having changed from an effective seat product just over 900 (consistent with moderate PR) to one of 650 (the same as the value for the UK) solely due to assembly-size reduction.

The effective number of seat-winning blocs is certainly in the ballpark of expectations under a majoritarian system, with 2.90 in 2018 and a drop to 2.40 in 2022 when the assembly size reduction makes it even more majoritarian. The reduction in 2022 occurs in spite of a slightly increased fragmentation of the vote, even at the bloc level (from 3.36 to 3.44). That is, of course, why the disproportionality is so high in 2022.

The bottom line result is that the center-right bloc obtained 59.3% of the seats on 43.8% of votes–a classic majoritarian outcome. In 2018, for comparison, it had 42.1% of the seats on 37.0% of the votes. Its votes grew by 6.8 percentage points, but its seats by 17.2. Some of that is due to the bigger gap between the top two two blocs this time around, which in turn was a product of the center-left’s less complete alliance formation, but a lot of it is the lower number of single-seat districts resulting from the cut in the Chamber size.

Based on the seat product model, by which we expect NS=(MS)1/6, and using the numbers reported earlier for effective seat product, we should expect the 2018 system to yield NS=3.12 and the 2022 system to yield 2.94 (based on effective seat products of 920 and 650, respectively). These are “politics blind” expectations, based solely on the systems’ fundamental design features–district magnitude of the basic tier and the sizes of the tiers that comprise the assembly. We can see that in both elections the actual outcome by blocs was a little less fragmented than these expected values, but not to any extraordinary degree. The calculation of effective seat product for these complex systems gets their impact on the assembly party system about right.

As I mentioned, I do think these indicators are more meaningful when calculated on party level for a system like this. The parties within a bloc coordinate nominations in the single-seat districts, and the contest over who will form the post-election government takes place between blocs. Thus the blocs are the meaningful units. On the other hand, nothing commits the parties within a bloc to continuing to work together, and they agree that the votes for list will determine which one gets the prime ministerial post if the bloc wins a majority. The parties thus remain relevant and competitive actors, too. The outcome at party level was a little less “blocky” overall this time, with more parties gaining significant vote and seat shares despite being outside a bloc.1 But even at the party level, what is likely to matter most–at least in the short run–is that the largest party within the largest bloc has a majority of its bloc’s seats (119 of 237 for the Brothers), despite only 26% of the overall vote for parties.2

All in all, the the key take-home outcome is that the MMM system strongly rewarded the parties that had coalesced to form the biggest bloc, and the largest party within that bloc. That is just as we would expect MMM to do, particularly with such a reduction in assembly size.

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  1. Five Star was in this category both elections. In 2018 it won 32.7% of votes and 36% of seats. This time it dropped to 15.4% of votes and 13% of seats. In addition, Action–Italia Viva in this election had 7.8% of votes and 5.3% of seats. More to the point, the three biggest blocs (counting Five Star as one of the “blocs”) had 92.5% of the votes in 2018 but just 85.4% in 2022.
  2. Quite different from 2018 when the League had just 47% of its bloc’s seats–which were in any case not a majority of the Chamber. The League’s party vote in 2018 was 17.4%.

Northern Ireland assembly-size and magnitude change

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A political agreement in late December in Northern Ireland includes a provision:

to cut the number of Assembly members from 108 to 90 and Executive departments from 12 to 9 and to allow for the formation of an opposition with effective speaking rights. In theory the creation of an opposition raises the possibility of a future alternative coalition. (Brian Walker, The Constitution Unit, 13 January)

Although Walker, in the cited piece, does not say so, it would seem this means district magnitude (M) will be reduced from six to five. There are currently 18 electoral districts, each electing six assembly members. Given a reduction of assembly size by 18, I will assume this means each district loses a seat.

The impact would be to make Northern Ireland’s elections somewhat less proportional, which is a goal consistent with Walker’s statement about the possibility of a future alternative coalition. That is, the political reforms, as a package, could be seen as representing a small step away from consociationalism (power-sharing) in the direction of majoritarianism (with its more defined government-opposition divide).

Based on the 2011 election results, one might surmise that the lone Green and TUV members, as well as the one independent, would be unlikely to retain their seats. The UUP would be unlikely to win two seats in Strangford on barely a fifth of the vote, as it did in the six-seat district, and might have trouble holdings its one seat in districts such as Belfast East, West Tyrone and Mid-Ulster. Sinn Fein likely would struggle to retain its seats in East Antrim (8.4% of vote) and Belfast South (12.5%). These are just examples of some potential losses, but one can’t be sure given that obviously the votes will not break down in the next election the same way as they did in the last, and I have not considered the distribution of preference flows (Northern Ireland uses STV). The general point is simply that larger parties, in any given district, should be somewhat favored by a reduction of district magnitude, particularly the move from an even number of seats in each district to an odd number. And this would tend to support, at least marginally, a move towards two alternative governing options, when combined with other changes.