The simple version is Labor Party supporters were more inclined to be straight-ticket voters, while those inclined toward the Liberal Party spread more of their votes among other parties.
That’s how the Labor and Liberal parties went from five seats each on the Longyearbyen Community Council, when there was a nine-vote difference immediately after the election, to Liberals losing a seat a day later in the official count, even though they narrowed the vote margin to a mere five ballots.
Beyond that, trying to explain the formula used to allocate seats or ponder “what-if” scenarios if a person (or three) had voted differently is easy to explain only (and then only maybe) if you’ve got a PhD in mathematics (and then only maybe). Or if you actually are familiar with something called the Webster/Sainte-Laguë method.
Under that method, Labor got 350 votes to Liberal’s 345, but the “quotients” were 3,782.857143 and 3,649.285714, respectively.
No, going to Wikipedia isn’t going to provide a summary allowing mere mortals to grok its logic and calculation formulas (unless the picture above makes sense). Nor does the Norwegian government’s English-language explainer of its Parliamentary election system, which Longyearbyen (and a whole bunch of countries around the world) also rely on. There are online and downloadable calculators, but be prepared to feed a lot more than just the totals for each party into them to get results matching what happens in real life.
But in practical terms, local voters select 15 candidates for the 15-person council. Each party places a ranking on its candidates (number one means that candidate is mayor if the party prevails, for instance, while a candidate that’s 10th on the list has no real chance at a council seat – although end-of-the-listers often end up on subcommittees and such). The formula uses a weighted system that factors in all votes for all candidates – in short, voting for those end-of-listers can provide extra seats even if those persons will never sit in them.
Here’s the key paragraph from the Norwegian government’s explainer, for anyone wanting to attempt to decipher it:
“The system is based on the principle that members’ seats shall be allocated proportionally to the parties/groups according to the votes cast for the individual electoral list. This principle is called proportional representation. The allocation of seats to the different lists is carried out by means of the same mathematical method for both parliamentary and local government elections. This method is called Sainte-Laguë’s modified method. This means that the number of votes polled by the individual list is first divided by the figure 1.4 and thereafter by the figures 3, 5, 7, 9 etc. By means of these divisions a number of figures are arrived at, quotients, as they are called. These quotients are arranged according to size. The members’ seats are allocated to the lists that have the largest quotients. The first seat goes to the list that has the largest quotient, seat No. 2 goes to the one that has the second largest quotient and so on.”