South Korea 2020

South Korea had its assembly election on 15 April, with various covid-19 precautions in place. The Democratic Party of President Moon Jae-in (elected in 2017) won a majority of seats.

As discussed previously at F&V, the electoral system was changed from mixed-member majoritarian (MMM) to, at least partially, mixed-member proportional (MMP) prior to this election. It is only partially MMP not mainly because the number of compensatory list seats is so small (30 out of 300 total), but because there remain 17 seats that are, apparently, allocated in parallel (i.e., as if it were MMM).

There was some discussion in various media accounts (and in the previous thread) of the major parties setting up “satellite” parties to “game” the MMP aspect of the system. Under such a situation, a big party will contest the nominal tier seats and use a separate list to attract list votes and seats. By not linking its victorious nominal candidates with a same-party list, a party can gain extra seats, vitiating the compensation mechanism that defines MMP. This is what happened in Lesotho in 2007, for example. (That thread has an interesting series of comments about the issue, including why German parties do not do this in their MMP system.)

The Democratic Party set up a Together Citizens Party to compete for list seats and the main opposition United Future Party set up a Future Korea Party to do the same.

However, if I understand the results correctly (at Wiki), it seems the satellite was not necessary for the Democratic Party to win its seat majority. The Democrats won 163 constituency seats on 49.9% of the (nominal) vote; with 300 total seats, this is a majority no matter what happens with the list seats. Their satellite won 17 seats on 33.4% of the list votes. The United Future won 84 nominal seats on 41.5% of the nominal vote; their satellite won 19 seats on 33.8% of the list votes. I am finding these numbers hard to understand! Maybe someone else can figure this out for us.

8 thoughts on “South Korea 2020

  1. For a president’s party to get almost half the votes nearly 3/5 of the way into the presidential term is… surprising. He won only 41.1% in his own election, in a three-candidate race. Normally, we should expect a significant decline. In fact, the estimator we use in Votes from Seats would expect only around 31%. On the other hand, it assumes a relatively stable party system. And when a country goes from three candidates getting over 20% of the vote for president to two parties combining for more than 91% of the (nominal) vote in the assembly election, we are clearly not dealing with a stable party system.


  2. The only sure way to stop decoy lists is to be willing to add as many “overhang” seats as it takes to restore proportionality (Germany?). Otherwise, even single-vote MMP can be gamed, but the potential gain is much smaller than in 2-vote MMP.


    • How can Single Vote MMP be ganged or have decoy lists? I had suggested using a 1 vote MMP with ranked choice voting only the first preference is the party vote or is there another way to design this.

      How many overhang or balance seats would be needed to restore proportionality for South Korea’s National Assembly?


  3. Gaming the system under 1-vote MMP requires an uneven distribution of electoral support. A party runs its A-list candidates in districts where the party believes its chance of winning is greater than 50%. Its decoy B-list candidates run in the other districts.

    A party’s excess seats come only from votes for unsuccessful B-list candidates, rather than from all of its partisans’ votes as is possible under 2-vote MMP. Any votes for unsuccessful A-list candidates are wasted. Parties might well conclude that gaming 1-vote MMP has too high a cost-benefit ratio.

    On reflection, adding overhang seats in 2-vote MMP can’t negate the advantage of a decoy list for any party strong enough to win single-member districts. If it is possible to win SMD seats with no associated Party votes, the seats-to-votes ratio is infinite and no amount of overhang seats can compensate. At the very least, there would have to be some forced linkage between the vote for an SMD candidate and the Party vote, as in the Bavarian system, for example.


    • If a country has a problem with decoy lists under a MMP system that mutates to MMM, they would be better off using a small to moderate district magnitude open party list system or Single Transferable Vote system. And to top that off with national levelling seats, but that usually isn’t done for STV.


  4. In this year’s legislative election in South Korea the People Party and the Open Democratic Party – which won 6.8% and 5.4% of the party list vote, respectively – didn’t contest SMD seats. Meanwhile, the third-placed Justice Party won 9.7% of the list vote but only 1.7% of the SMD vote. The votes cast for these parties appear to account for much of the large differences between the results obtained by the major parties in the SMD races, and those polled by their “satellite” parties for the PR seats.

    It should also be noted that elections to Japan’s House of Representatives in the past decade have shown similar large variations between the SMD and PR list outcomes: in 2014 the ruling LDP won 48.1% of the SMD vote, but only 33.1% of the party list vote, largely because its ally New Komeito won just 1.4% in the few single-member districts it contested, but 13.7% in the race for PR seats, where it ran everywhere in the country.


  5. Pingback: Is Scottish MMP being “gamed”? | Fruits and Votes

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