Parallel Systems

Parallel systems also use both PR and plurality/majority components, but unlike MMP systems, the PR component of a parallel system does not compensate for any disproportionality within the plurality/majority districts. (It is also possible for the non-PR component of a Parallel system to come from the family of ‘other’ systems, as in Taiwan which uses SNTV.)

In a Parallel system, as in MMP, each voter may receive either one ballot paper which is used to cast a vote both for a candidate and for his or her party, as is done in South Korea (the Republic of Korea), or two separate ballot papers, one for the plurality/majority seat and one for the PR seats, as is done for example in Japan, Lithuania, and Thailand. Parallel systems have been a product of electoral system design over the last decade and a half—perhaps because they appear to combine the benefits of PR lists with those of plurality/majority (or other) representation.

Advantages and disadvantages of Parallel systems

Advantages of Parallel Systems

In terms of disproportionality, Parallel systems usually give results which fall somewhere between pure plurality/majority and pure PR systems. One advantage is that, when there are enough PR seats, small minority parties which have been unsuccessful in the plurality/majority elections can still be rewarded for their votes by winning seats in the proportional allocation. In addition, a Parallel system should, in theory, fragment the party system less than a pure PR electoral system.

Disadvantages of Parallel Systems

As with MMP, it is likely that two classes of representatives will be created. Also, Parallel systems do not guarantee overall proportionality, and some parties may still be shut out of representation despite winning substantial numbers of votes. Parallel systems are also relatively complex and can leave voters confused as to the nature and operation of the electoral system.