The Herald piece on National's plans to replace MMP with the unfair Supplementary Member system claimed that it was "described as having "real merit" by the 1988 [sic] Royal Commission which eventually recommended MMP". Hardly. Here's what the Royal Commission really said about SM (from Chapter 2 of their 1986 report):
2.103. Fairness between political parties. SM is not a proportional electoral system, and therefore does not attempt to overcome many of the problems inherent in plurality in single-member constituencies. the fact that only the additional seats are allocated proportionally and without regard to the results of the constituency elections means that the total seats won by a party are likely to remain out of proportion to its share of the votes. That this is so for both major and minor parties is illustrated by table 2.3, although we stress again that we have had to assume that list votes would got to parties in the same proportions as constituency votes. The figures for Labour and National for 1972, 1975 and 1978 illustrate the point in stark terms; there would still have been a considerable imbalance between share of the votes and share of the total seats. In a close election where the party with the most votes gained fewer constituency seats than another party, it would be unlikely that SM would significantly improve the result.Describing that assessment as "real merit" is like describing the Electoral Finance Act as "an assault on democracy". But then, it's pretty clear from their other mistakes that the Herald didn't actually bother to check the report first, but simply recycled the "facts" from National's press release verbatim. And they call themselves "journalists"...2.104. It is true, however, that minor parties would do better under SM than under our present system, and so in that respect SM might be said to be "less unfair" than plurality. That it is nevertheless still unfair to minor parties is shown by looking at the relationships between seats and votes for Social Credit over all 6 elections, and for the New Zealand Party in 1984. These parties would achieve better representation but still pay a heavy penalty because of their difficulties in winning constituency seats.
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2.114. Conclusion. The Commission recognises that SM has considerable appeal. It improves on the plurality system in a number of ways. First, it would give representation to significant minor parties. Second, because almost all of the list votes would count towards the election of candidates, electors in safe seats would have a more effective role than under the present system. Third, it would enable the parties, particularly major ones, to protect a limited number of particularly able members in marginal seats. Fourth, it would provide a way of increasing the number of MPs but avoid the disruption to constituency boundaries that would be caused by a significant extra number of single-member constituencies. Fifth, it would, because of the list, be likely to enhance the representation of Maori voters as well as voters belonging to other special interest or minority groups. Sixth, it would lessen somewhat the disproportionality between major parties.
2.115. Nevertheless, the Commission is of the view that SM does not go far enough in meeting the fundamental objections to the plurality system in respect of the relationship between seats and votes. Those objections would still be powerful under SM, even though minor parties might be somewhat better off. We are reluctant to rule out SM altogether, however, until we have seen whether either MMP or STV can overcome the objections to both plurality and to SM without introducing too many disadvantages of their own.
