[EM] Preferential voting system where a candidate may win multiple seats

[Juho Laatu]

On 19.7.2013, at 10.18, Kristofer Munsterhjelm wrote:

> In short, multiple constraints might mean that the results "over here" depends on what happens "over there" in a way that's not easy to understand. And the more constraints you add, the harder it could get.

One could estimate the level of confusion caused by those properties of the method that are not very easy to explain by studying the complex properties of the current system. In Norway the leveling seats are one potential topic. Could a discussion on the leveling seats go like this? "Why do we have leveling seats?" "To make the results more balanced." "Ok." If this is plausible, and if people thus accept the current level of complexity in the rules, then people could accept same level of complex rules also in the new system. The "acceptable explanation" could refer to the algorithm itself or to the design principles behind the algorithm.

> In such cases, I would also suggest a few of the seats of the parliament be given by a centrist- or minmax-based method (e.g. Condorcet, CPO-SL with few seats, or possibly even minmax approval or something like it). The idea would be that there shouldn't be any kingmakers, but if there's a near-tie, that tie is broken by a moderate group.

In proportional systems one should distribute most of the seats directly to different parties without seeking for compromise candidates. I mean that also extreme parties should get their proportional share of the seats. Only in the allocaton of the very last seats (=last seats at national level) one can take the second preferences of the voters into account. The second preferences often point to compromise oriented candidates (by definition). The idea of favouring compromise candidates thus means taking the second preferences of the voters into account when allocating the very last seats.

Sometimes the voters may prefer giving the last seat to a compromise party (with only a small fraction of quota of first preference votes supporting this decision) to giving it to one of the main parties (that might have close to 0.5 quota of first preference votes left supporting their candidate). The CPO approach is a good way to estimate which allocation of seats would get wide support among the electorate.

Juho