Report on the 2017 Presidential Election in Chile
The goal of this special report is to examine the performance of opinion polls in the Chilean presidential election of November 19, 2017. In the first round election, all the pre-election polls overestimated the vote share of the winner, Sebastian Piñera and significantly underestimated the vote share of the candidate who finished in third place, Beatriz Sánchez, generating a lot of controversy about the polls. The candidate who finished in second place, Alejandro Guillier, was well estimated. The performance of the polls in this case, as in many other elections elsewhere in the world, had an impact in the overall credibility of the polling profession and polling data in Chile, as reported below. It is therefore important to understand not only the various reasons why polls may get it wrong in a particular election but also what we might learn about the general conduct of polls and how they are reported that could improve their conduct and use in the future.
The World Association for Public Opinion Research (WAPOR) was asked by some of its members in the region to set up a special committee to document the record of the polls that were published, offer information about polls that were not published but were shared with the WAPOR special committee by some polling firms as a resource to find explanations for possible biases, and provide an in-depth discussion of various sources of error that may have contributed to misestimates in the polling. Those sources include both methodological aspects of the polls, as well as legal and contextual aspects of their publication, such as recent changes in election laws regarding compulsory and voluntary registration and voting as well as the enactment of a 15-day ban on the publication of polls before Election Day.