It is effectively impossible for the public to vote out politicians who rank highly on one of the major parties' lists. This year New Zealanders have a say on whether to change the MMP electoral system, with a second vote being held in 2014 to choose the new electoral system if a majority of electors vote for a change.
A fundamental test of an electoral system is whether it fosters a sound and prosperous democracy. Since no system is perfect, the advantages and disadvantages of each system need to be carefully compared and assessed.
MMP replaced the long-standing First Past the Post system from the 1996 general election onwards. Our choice now can therefore be informed by 15 years of local experience. Experience shows New Zealand made a mistake when it departed from one of the world's oldest parliamentary systems.
Under MMP, political parties make deals at the expense of taxpayers. The first coalition agreement between National and New Zealand First entailed a $5 billion spend-up. This set the pattern that has applied since. It is disturbing in this context that core Crown spending increased from 29 per cent of GDP to 35 per cent of GDP between 2005 and 2011 under MMP.
What this means is that under MMP the leaders of small political parties, such as Winston Peters, effectively choose who governs based on what the two large parties will offer as part of a coalition agreement. The public, of course, picks up the tab.
Worldwide, the results are similar. Government spending is around 5 per cent of GDP higher in countries with proportional representation systems. This matters, because high spending and taxation are a drag on growth.
MMP also entrenches established politicians.
It is effectively impossible for the public to vote out politicians who rank highly on one of the major parties' lists. Under MMP, the party machines decide much of the composition of the House of Representatives, not the voting public. MMP has the regrettable consequence of conferring job protection on any politicians regarded as under-performing, even though they may have no prospect of persuading any electorate to vote them in.
The eminent Philosopher Karl Popper suggested that a decisive test of any political system should be how well it allows an electorate to get rid of a bad government by voting it out of office.
MMP fares poorly under this test. Under a system of coalition governments, the electorate might think it has voted a government out of office on election night, only to find that through coalition negotiations it is still the government.
In 1996 New Zealand First campaigned in good part on the slogan that a vote for it was the only way voters could keep the then National government out of power. Yet its leader, Winston Peters, in the end handed National another three years in office to the dismay of many of its members.
MMP commonly produces weak governments with feeble mandates. Fragile minority governments are also more common under MMP. Decision-making is slow and compromised by the deal-making necessary to obtain a majority. As a result, effective decision-making is more difficult.
Australian journalist Janet Albrechtsen recognised these problems with MMP when she observed, "Forget democratic principles of voters knowing what they voted for and politicians being accountable for their promises. Post-election horse-trading between minor parties and minority governments will mean election promises count for nought."
In comparison, under FPP, the voters choose who represents them, not the party machines. Voters usually know exactly which party to hold to account for the government's performance. Election night outcomes are commonly clear-cut, allowing strong governments with solid mandates. Coalition governments can arise but such outcomes are the exception rather than the rule.
The main argument advanced in favour of MMP is that it provides for wider parliamentary representation of a diverse community than FPP. This is a doubtful argument.
While the gender and ethnic diversity of members of Parliament has increased since MMP was implemented, greater diversity would have occurred anyway (as it has everywhere else in society).
Another claimed advantage of MMP is that it would permit political parties to bring highly qualified people into Parliament who might be put off by the need to contest an electoral seat under FPP. A handful of parliamentarians could arguably come within this category. There is, of course, a risk of the opposite outcome - of people with no special talents and who are overwhelmingly rejected in contests for electoral seats, able to enter Parliament as list members.
MMP concentrates power in the hands of central party hierarchies that draw up the party lists. This departs from the Westminster tradition which holds parliamentarians responsible to their electorates, not their parties.
In summary, MMP should be changed. FPP would be better for democracy and for New Zealand's prosperity.
Roger Partridge is the chairman of the New Zealand Business Roundtable.