Some pollsters ask how likely one is to turn out to vote.
Amongst those that do, they weight responses differently.
Some will only report those who are 10/10, 9/10 and 8/10 likely to vote in their topline figures.
Some will multiply the likeliness with the voting intention, so that a 10/10 likely voter would count as a whole vote, a 9/10 likely voter as 9/10ths of a vote and so on.
The UK Polling Report[0] - run by the guy in charge of YouGov, if I recall correctly - is a very useful site for explaining UK polling oddities!
Amongst those that do, they weight responses differently.
Some will only report those who are 10/10, 9/10 and 8/10 likely to vote in their topline figures.
Some will multiply the likeliness with the voting intention, so that a 10/10 likely voter would count as a whole vote, a 9/10 likely voter as 9/10ths of a vote and so on.
The UK Polling Report[0] - run by the guy in charge of YouGov, if I recall correctly - is a very useful site for explaining UK polling oddities!
[0] http://ukpollingreport.co.uk/