SOURCES
The FT’s main UK poll tracker uses data from every new national voting intention poll by a member of the British Polling Council. Voting intentions in demographic subsamples use data from Deltapoll, Ipsos, Omnisis, Opinium, PeoplePolling, Redfield and Wilton, Savanta, Survation, Techne and YouGov.
METHODOLOGY
We use general election polls covering the United Kingdom or Great Britain to calculate both an average voting intention and a range of likely values for each party.
To compute the average at a particular moment in time, we take every poll released in the last 14 days, and assign it a weight based on how long ago it was released, its sample size, and how frequently the pollster releases polls. The moving average is the weighted mean of these polls.
Polls are first weighted according to an exponential decay function, so that a poll released today is weighted fully, while a poll released two weeks ago is not weighted at all. Polls with larger sample sizes are also weighted…