When there are votes for parties that didn't make it into parliament ('sub-votes'): -
Proportion of seats = Party-vote %/(100% - sub-votes%)
This election the sub-vote added up to 6%.
National's proportion of seats is (48.1/94) = 51.2%.
51.2% of 121 seats is 61.9 seats.
National got 61 seats. The 0.9 seat mismatch is because it isn't actually that simple. A quotient formula is used, that iteratively allocates seats. This method in effect slightly favours smaller parties.
ubergeeknz:bazzer:joker97: if a party wins 4.9% of party vote and doesn't get into parliament wheredo the seats go to?
I believe the 120 seats get allocated based on your percentage of the "useful" votes. So, I suppose, the 4.9% would get shared equally amongst the other parties in proportion to their party vote.
Yep, those votes are "lost" - as if they were never cast. Then the proportion is worked out from the remaining votes.