Why Do Voters Lie to the Pollsters?
| DOI | 10.1177/2041905816637454 |
| Date | 01 April 2016 |
| Author | Paul Whiteley |
| Published date | 01 April 2016 |
16 POLITICAL INSIGHT • APRIL 2016
In the months running up to last May's
General Election, opinion polls predicted
a tight nish, with both Labour and
Conservatives falling far short of an overall
majority. But on election night, the exit poll told
a very dierent story: Conservatives had won,
Labour was trounced. In the aftermath, the
British Polling Council initiated an inquiry into
this polling failure with the aim of discovering
what went wrong.
Table 1 shows that eight dierent survey
agencies understated the Conservative vote
by an average of 4.2 per cent and over-stated
the Labour vote by 2.4 per cent in their nal
pre-election surveys. These discrepancies in
the polls can be explained by a wide variety
of dierent factors, including problems with
research designs, sampling, survey modes,
inaccurate voter registration, and also
diculties in the recording of survey answers.
In this article I will concentrate on one factor
which may help to explain the problem; the
fact that some respondents gave misleading
answers to interviewers in the pre-election
surveys about their participation in the election.
This is described in the literature as ‘over-
reporting’. One of the great advantages of an
exit poll is that everyone in the survey actually
voted, since they are approached by researchers
outside the polling station. This is not true for
respondents in pre-election polls. If pollsters
interviewed a number of individuals who
claimed they were going to vote but in the end
did not, that could contribute to inaccurate polls.
Over-reporting Electoral Participation
There is a long history of survey methodologists
worrying about whether people tell the truth
For months ahead of last May’s UK General Election, polls predicted
that the outcome was too close to call. On the day, the result was
clear-cut. How did the polls get it so wrong? Paul Whiteley examines
one reason: over-reporting.
in polls. An early paper on this issue published
by Herbert Hyman in 1944 was titled simply
Do
they tell the truth?
and this question has been
repeatedly asked ever since2. This is thought to
be a particular problem in surveys asking about
sensitive topics such alcohol consumption, drug
use and sexual behaviour. But it has also been a
longstanding issue about whether people vote
in elections, which arguably is not an overly
delicate subject. Despite this, there is ample
evidence to show that individuals do overstate
their electoral participation. In a report written
in 1968, which compared survey data from the
American National Election Study with electoral
records, Clausen concluded that: ‘Estimates
of turnout have consistently exceeded the
population gures by about 12 to 13 per cent’1.
In the case of the UK we can use the 2010
face-to-face British Election Study survey data
to investigate this issue3. This was a probability-
based panel survey which interviewed the same
people before and after the election, and asked
about voting intentions and, subsequently,
voting behaviour. In addition, eldworkers
veried if their respondents actually did vote
Why Do Voters Lie
to the Pollsters?
Political Insight April 2016.indd 16 04/02/2016 10:54
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