Seats at large are intended to even out the distribution of seats. A seat of large is meant to equalise any skewing of representation after the constituency seats have been distributed.
Given how the Norwegian electoral system is designed, every vote counts in determining which party will receive one or more of the 19 seats at large. However, not all parties that stand for election will qualify to compete for the seats at large.
Why is the election threshold important?
It is almost impossible to follow an election campaign or read an opinion poll in Norway without realising that the election threshold is important, although it is not always easy to understand why it is important. Every party that puts up a list enjoys a level playing field in the competition for directly-elected constituency seats. If a party polls enough votes to win a directly-elected constituency seat in a county, they will enter the Storting even if they do not poll a single vote in another county. However, only parties that attract at least 4 per cent of the national vote can be awarded seats at large. Parties that attract fewer votes are not in contention for seats at large. That is why the election threshold is so important.
The actual calculation: rigid rules and cold mathematics
Determining how many seats at large each of the parties that exceeded the election threshold has won takes several calculations/steps.
First, one has to calculate which parties should receive seats at large and how many they should get. This is done by calculating a new electoral count in which one distributes all of the 169 seats, although this time using the entire country as a single constituency. This distribution is based on same method used when county electoral committees distribute constituency seats, i.e. the modified Sainte-Laguë method.
The number of seats the parties get in this new count is compared with the number of constituency seats already distributed to them. The difference between the two counts is the number of seats at large the parties should get. If the difference is negative, i.e. the party is already 'overrepresented', the calculation must be carried out again without including this party. The seats they have won are excluded from the process.
Thereafter, one must determine in which counties the parties should get their seats at large. One first calculates a county factor, which is the number of valid votes polled in the county divided by the number of constituency seats. For example: if 100,000 votes were cast in the county and 10 constituency representatives elected, the county factor will be 100,000/10 = 10,000.
Next one takes the parties' total vote polled in the county. If the party did not win any constituency seats, one uses the actual total vote polled. If the party has won constituency seats, the total vote polled is divided by a quotient that corresponds to (number of constituency seats x 2) + 1.
Finally, the total vote polled or quotient must be divided by the county factor
This calculation is carried out for all parties that should receive seats at large in all 19 constituencies. This results in a series of figures, one for each party in each county. These figures are then ranked from highest to lowest and provide the basis for distributing the seats at large.
The first seat at large is distributed to the party and the county with the highest number. The second seat at large is distributed to the party and the county with the next highest number and so on.
Once a county has been distributed a seat at large it is out of the competition. The same applies when a party has been distributed its full complement of seats at large. The distribution process continues for the remaining counties and parties until all 19 seats at large have been distributed.
Because seats at large are calculated based on the total vote polled from across the country, the calculations cannot be carried out before all of the counties have finalised their numbers. The calculations are carried out by the national electoral committee after the county electoral committees have certified their respective county electoral counts and distributed the constituency seats.