Peter Kellner examines the reasons why the pollsters so badly underestimated the Tory vote in the 1992 election and asks whether it could happen again.by Peter Kellner / May 20, 1996 / Leave a comment
Published in May 1996 issue of Prospect Magazine
British journalism review
Every single poll on election morning, 9th April 1992, predicted a hung parliament. Using very similar methods, they offered very similar figures-ranging from a Labour lead of 3 points (Nop), to a Conservative lead of 0.5 points (Gallup). Never before had the polls been so far from the true result: a Tory victory by 8 points.
According to a subsequent inquiry by the Market Research Society, the polls made a series of small errors which had the effect of inflating Labour’s rating and reducing that of the Tories. The inquiry claimed that none of these errors were individually large; what was deadly was their cumulative impact.
Since 1992, pollsters have agreed about one specific failing at the last election, and disagreed about almost everything else. They agree that their samples contained too few middle class ABC1s and too many working class C2DEs. All the polling organisations have increased their proportion of ABC1s from 41-43 per cent to 47-48 per cent, and ICM, Nop and Mori have also adjusted both their samples and their final figures. But some problems remain.
Apart from its monthly quota polls for the Sunday Times, Nop conducts three random polls each month, in which interviewers are given names and addresses of specific electors drawn at random, and required to track down as many of them as possible over a seven-day period. Between September and December, they found that the Conservatives enjoyed a 5 point lead over Labour among AB voters (professional and managerial workers and their spouses) who comprise around 20 per cent of the electorate. Yet Nop, Mori and Gallup quota polls all showed Labour ahead among these voters. In Nop and Mori polls the leads were generally small; but Gallup showed Labour ahead among ABs by 10-15 points.
My own hunch is that when interviewers conduct quota polls, they tend to target the “easier” AB voters; they conduct street inte…