Does the Tail Wag the Dog in Proportional Representation Systems?
In response to my TCS article and blog post yesterday on why the US has maintained a Democrat-Republican two party system since 1860 and likely would for the foreseeable future, UCSD political scientist Mathew Shugart, co-author (with Rein Taagepera) of the award-winning Seats and Votes: The Effects and Determinants of Electoral Systems, offered some interesting thoughts, including a throwaway line that he would “consider it a gift from on High for PR to suddenly appear in the US.”
I expressed some surprise in the comments section, because I had always thought the likelihood of the “tail wagging the dog” overrode whatever value proportional representation systems might offer. In today’s response, he argues that this is largely a myth.
Basically, there just is not much evidence that small parties get more than their weight in votes would entitle them to, nor that they are able to hold “hostage” the bigger parties (which, after all, are also minority parties that get, by definition, disproportionate influence under plurality elections!). And if it does not happen in Israel (where the largest party often has only a third of the votes and seats, the country is a single 120-seat district, and a party can win a seat with just 2% of the vote) it is unlikely to happen almost anywhere.
He cites a May 2005 study of Israeli politics from 1977-2003. Considering that Israeli is, along with Italy and the French 4th Republic, among the classic cases always cited for the “tail wags the dog” phenomenon, that’s pretty damning.
Apparently, every once in a great while, empirical studies in the social sciences actually teach us something!