The Hong Kong government recently announced a proposal to change the way they fill vacant seats in the Legislative Council. Hong Kong elects its MPs through open list proportional representation; the current method of filling a vacant seat is through a special election. While this seems somewhat intuitive, a special election is actually inconsistent with the values of a PR system. Awarding seats proportionally only really works if you have multiple seats up for grabs at once; otherwise, it just becomes a standard SMD race where the two largest parties will dominate. Most countries fill empty seats by picking the next in line candidate on the previous office holder’s party list. The new Hong Kong proposal, however, is to replace the vacant seat with the first unelected candidate on the party list that had highest number of remainder votes in the previous election. What does this mean? Proportional representation systems rely on quotas to evenly allocate seats to each party. This works by using as system where each seat in a legislature corresponds to a raw number of votes, equal to a quota. A party’s total seat total then, depends on the number of quotas it wins in an election. Although there are various ways to allocate seats (largest remainder or highest average method) no PR system can perfectly award seats in one-to-one relation to vote shares as leftover votes are bound to exist. Giving the seat to the first candidate on the list with the largest remainder then, is essentially giving it to the first candidate who did not win a seat in the last election.
A Government spokesman said, “A vacancy arising mid-term in the geographical constituencies (GCs) or the newly established District Council (second) functional constituency (DC (second) FC) seats will be filled by reference to the election result of the preceding general election. The first candidate who has not yet been elected in the list with the largest number of remainder votes in the preceding general election will be returned. These constituencies adopt the proportional representation list voting system. The proposed replacement mechanism is consistent with the proportional representation electoral system and reflects the overall will of the electors expressed through the general election.”
This is interesting because it assumes that individual candidates are driving vote choice more than party label. There are five constituencies in Hong Kong for thirty seats, so the average district magnitude any party list competes on is around five or six. I’m guessing this small district magnitude is what’s leading them to conclude that personalities matter. Hong Kong uses the Hare quota to allocate seats, the simplest method of seat allocation and one that generally favors smaller parties. As Hong Kong seems to return several small parties to parliament with one seat each, maybe they assume that the individual candidate who captured that seat was a big reason for the party’s success. To me this is contrary to what the literature would suggest. According to Carey and Shugart, low district magnitude in open list PR decreases the incentive for a candidate to cultivate a personal vote. In contrast, it is in high magnitude, open list PR where candidate preference matters more. This is because in a larger list, candidates have a stronger incentive to distinguish themselves from their fellow list members. Ultimately, we don’t really know why any individual is voting the way they are, but I think the Hong Kong government’s assumption requires more explanation.