Date post: | 13-Apr-2017 |
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News & Politics |
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Predicting Polling Failure
Matt SinghNumber Cruncher Politics
@MattSingh_ | @NCPoliticsUK
www.NCPolitics.UK
Bio – Matt Singh• Background in Finance and economics• Started Number Cruncher Politics Sep 2014• Aim is to spread the understanding of polling
and elections to a wider audience
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1992 revisted• The reason for my instinctive skepticism• Polls pointed to a narrow Labour lead, but
result was a Conservative overall majority• Net error of 9 points
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The spiral of silence• Observation: In phone polling, don’t knows
break for the party they voted for previously• In 1992, majority of supposedly undecided
voters had voted Conservative in 1987• This year, some polls found a similar pattern
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Divergence from fundamentals• “I can find no example of a party losing an
election when it is ahead on both leadership and economic competence”
– Peter Kellner, YouGov President, April 2014
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Current thinking – what it’s not• Late swing• Herding• Sabotage
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Current thinking – turnout?• Likelihood to vote questions implied a turnout
of over 90% in some cases• Actual turnout was 66%• No shows may have been unrepresentative• Evidence of people lying about having voted
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Current thinking – wrong answers?• Evidence of people lying about having voted• Might they also lie about how they voted?• Some inconsistencies in answers
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Current thinking – sample imbalance?• Some unexplained patterns in microdata…
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Using polling – house effects• Systematic difference between pollsters’
results owing to methodological differences• Can be interpreted as the difference two
pollsters would get in identical conditions
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Using polling – don’t know, do care• Some people answer, but many don’t• Don’t knows can vary substantially between
pollsters• Don’t knows can be heavily biased
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