Determinants of polling accuracy: the effect of opt-in Internet surveys

<p>With the changing polling environment and the difficulties in correctly measuring public opinion, it is crucial to study the effects of polling practices. Elections provide an opportunity to examine how well polls measure support for political parties and how polling practices influence the accuracy of polls. Based on 110 pre-election polls conducted in Sweden, a multiparty system, we find that probability-based samples yield more accurate polls compared to opt-in Internet samples. Thus, our results point to a tradeoff between inexpensive online polls and accuracy.</p