projections2015.ch projects the percentage party strengths, from which it derives the distribution of seats in those 15 cantons that had five or more seats in 2011. Tessin canton is projected separately and integrated into the national projection. Initial projections for individual cantons are expected immediately at 12:00pm, with a projection of party strengths and numbers of seats across Switzerland becoming available at 7:00pm.
The projections are based not on voter polls but on real voting results. In the individual projection cantons, the party votes of the first municipalities to declare are compared against the data from 2011 and projected for the canton as a whole. In cantons that count the voting papers first, the projections are initially based on these data in an initial round. Naturally, the voting power of the municipalities is weighted. The projections for the individual cantons show the party strengths as a percentage, from which the distribution of seats is derived. For the projection for Switzerland as a whole, which is issued at 7:00pm, the definitive results of one canton are combined with the projections of the remaining cantons.
Although the large number of parties and lists makes election projections in Switzerland more challenging than in other countries, the projections team has previously produced projections that were very close to the final results.