physics and voting systems

July 27th, 2007 by myrta

When back in Italy it is unavoidable to get involved in Italian politics. This time – I have been in Italy the first two weeks of this month – wasn’t an exception. And this time the matter of the politicians’ squabbles was the vote of the senators-for-life. In fact, since the difference of seats between the government and the opposition coalitions at the Senate is minimal, the vote of the senators-for-life has been, and could be in the future decisive in several occasions. That reminded me of an article I read last year on Le Scienze, the Italian edition of Scientific American on the recent reform of the electoral system of the Italian Senate. This reform introduced a bonus for the coalition with the majority that in principle should enhance the governability and stability. In practice, the authors of this article – researchers in Physics of Complex Systems (that’s where the title of this post is coming from)- show that the effects of this reform are unpredictable, and the “bonus” can increase, decrease or let as it is the number of seats of the majority coalition (this has indeed been the case in the last elections). The reason is that the bonus is given on regional basis. In brief, the authors remark that the actual voting system for the Senate resembles the behavior of chaotic systems which have a deterministic trajectory, but since this trajectory depends on tiny details, can’t in fact be predicted.

Recently signatures have been collected to promote a referendum to change the voting system for electing the Senate. The quota has been reached so probably, if nothing happens in the meanwhile, we will have a referendum (yet another one!) to change the electoral system for both the Parliament and the Senate. That brings me to this second article (that was referred by the previous one, not a physicist this time). The starting point is that while the citizens should choose the electoral system, this choice is technically too involved, and in fact the citizens cannot make this choice directly. As a solution the author suggests that the citizens simply choose what are the values of two parameters related to the representativeness and governability, then the electoral system corresponding more closely to this choice is selected via a purely technical procedure.

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