All this just shows Kiwi's don't understand the system we use to elect members to parliament. It's called MMP but the system is the Sainte-Laguë method. This is not a percentage of the vote = number of seats system. If it was then National's 47.31% of the vote translates to only 56 seats not 59.
The Sainte-Laguë method uses a mathematical calculation to rank votes in order of 1 to 120 for all parties and then allocates 120 seats in order of highest vote quotient downwards. eg on 26 November - National got seat 1, Labour seat two, National seat 3, Greens seat 4, National seat 5, Labout seat 6 and so on.
The Sainte-Laguë calculation is Quotient = V / 2s + 1 ... where V is the total votes each party got and s is the number of seats in a parliament sequentially increased from 0 to 120.
So National got 1,058,638 votes ... 1,058,638 / 2x0+1 = 1,058,638 this is first vote quotient. 1,058,638 / 2x1+1 = 352.879 this is second vote quotient and so on ...
The final result is a table that allocates all 120 seats and is why when special votes came in National lost a seat and the Greens gained it.
Any review of MMP's proportionality would need to review the method we use for MMP