Both houses of the Chilean legislature have passed legislation to increase the size of both chambers and scrap the current electoral system.
The assembly size changes are modest. Chile currently has one of the smallest first chambers, relative to population, of any democratic country (see graph). The planned change from 120 to 134 will redress this only slightly. The Senate will go from its current 38 members to 44.
The current electoral system for both houses tends to be referred to by the rather uninformative name, “binomial” system. It is open-list PR in two-seat districts, using the D’Hondt formula. D’Hondt is probably the most common PR formula, but of course it isn’t very proportional when your district magnitude is two. It does, however, tend to over-represent the second largest list, usually the conservatives, and this was its intention. (Aside: I met someone in the US government in about 1988 who had served as an advisor to the Chilean government, and he said the goal of the system then being designed was, in his words, “to screw the left”. Interesting that it is a conservative government that is finally moving ahead with changes.)
The article does not make clear what the new system will be. Presumably PR with higher and variable magnitude. Or maybe the same M=2 districts but with the additional seats being for a national compensation tier. If anyone has details on either the planned new system or the politics behind it, please comment.
The new system will not be in place until the 2017 elections.
(H/t to Chris, in an earlier thread on the topic; yes, they’ve been talking about this for a while.)