What are elections for? Conferring the median mandate

Democracy is often described as a system in which a majority of electors choose one out of a number of competing parties to form a government and carry out its programme. Unfortunately, spontaneous majorities rarely form in support of one party. We generalize from a 'government' to a 'median' mandate, in which the median elector chooses the pivotal party in parliament, which then translates his or her preferences into public policy. To check this we investigate how accurately parliaments and governments represent the left-right position of the median voter in each of twenty parliamentary democracies. Distortions depend on the type of electoral arrangement, being relatively smaller under proportional representation than under single-member districts. Distortions do not equate to biased representation, however. Once we consider how distortions at one step or one time are compensated by distortions in the opposite direction at another, overall representation of the median voter position is reasonably accurate.