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

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
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.


  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

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.