Turnout decline in Britain is greater than it first appears since changes in the social composition of the electorate have had a positive impact on turnout. This paper finds that whereas a weakening in the strength of party identification is associated with the long-term decline, the political context influences short-term variation. Partisan dealignment is also changing the dynamics of the determinants of turnout. Since non-identifiers are more strongly influenced by the political context than strong identifiers, and there are now more non-identifiers than previously, the political context is becoming a more important factor in determining whether people vote or not.