Poll Methodology, Weighting and Adjustment Systems

Abstract

In the 2005 General Election campaign the polls all ended up saying more or less the same thing. In the final round of published pre-election polls by BPC members, we were very close in our estimation of the Great Britain vote share for each party (see Mortimore and Atkinson’s chapter, Table 11.2). There were, however, marked differences between the polling companies in how they arrived at these figures: between them the BPC member organisations used three different fieldwork methods during the election campaign, and no two companies apply exactly the same weightings and adjustments to their data before publication, indeed there are some marked differences and — in terms of polling methodology — we cannot all be right.