Results : 3. Why did the polls go wrong?
Most pollsters use sampling frames in which unlisted telephone numbers are not included and these people are more likely to be Liberals
Those who refuse to be interviewed are more likely to be Liberals
The proportion of people living in collective households (old age homes, etc) is rising and it is not taken into account by adjustment weighting. These people vote in greater proportion for the Liberal Party
All biases act in the same direction: underrepresentation of the Liberals