ASA Connect

RESPONSE BIAS IN ELECTORAL POLLS

On the eve of the Presidential Election, pollsters are flooding us with electoral polls. Because it is known that, among others, polls act as an advertising resource for the presumed winner, polls' users – the voters - should be warned about known biases in such polls. "Literature supports that social desirability and acquiescence bias is significant in interview type modes rather than in self-administered modes" (Heather Hisako Kitada, Reed College and Oregon State University; Kaelyn M. Rosenberg, Reed College, "Exploring Data Quality and Time Series Event Detection in 2016 US Presidential Election Polls", CSP 2018). A wide literature is available about and I refer readers to it for more details and for hints to manage this critical problem.

In summary,

1. Social desirability bias is due to respondents who decline to answer or even modify their answer in order to shield themselves from interviewers' blame. In a bold contraposition like the current one, the fear to face consequences or simply to be considered not in the main stream due to the given answer can be greater than usual. Even if the interviewer could be a machine, interviewees can still feel ashamed in supplying their voting intention for the candidate out of the mainstream.
2. Acquiescence bias is due to respondents' compliance attitude whereby they agree with interviewers' perceived opinions. Incredible as it may seem, respondents perceive which response the interviewer is expecting to get.

Beyond these two, I suspect that in this moment a new bias in on the rise. I call it the Opportunity bias. Though still not enough considered by pollsters, it appears to me real, however. Likely voters who want to take the opportunity of a poll to send their true candidate a non-satisfaction message may provide an instrumental punitive vote's intention. Therefore, trailing candidates in the polls should deepen the reason of their trailing condition. May be, their voters want the candidate to move further right or further left. In the real situation of voting, everybody will come back to his true candidate, anyway, even if his punitive message didn't get much attention from him.

In my opinion, this time pollsters have a very tough job because, among others, an efficient solution for correcting these biases is still in its infancy.