The Representativity of Election Polls

Abstract

AbstractElection polls are conducted in many countries during election campaigns. Provided such polls are set up and carried out correctly, they can give an accurate indication of the voting intentions of people. However, the last couple of years these polls seem to be less able to predict election results. Examples are the polls for the general election in the UK of 2015, the Brexit referendum in the UK, and the presidential election in the US of 2016. The polls in the UK and the US have all in common that they are either telephone polls or online polls. It is shown in this paper that both type of polls suffer from lack of representativity. The compositions of their samples differ from that of the population. This can have several causes. For telephone polls, problems are mainly caused by increasing nonresponse rates, and lack of proper sampling frames. Most online polls are based on samples from web panels that are recruited by means of self-selection instead of random samples. Such web panels also not representative. The paper analyses the shortcomings of these election polls. The problems are illustrated by describing the polls in the UK and the US in some more detail.