A quick explanation for people who are new to pouring over the details of polls and, as several people have commented, are confused by the conflicting figures given for whether a party is up or down and if so by how much in a poll.
Different polling companies use different methods, so comparing – say – an ICM poll with a previous BPIX poll isn’t comparing like with like. Therefore when looking at a poll it makes sense to calculate up/down figures based on the previous poll by that polling firm.
However, polling firms often do work for more than one media …



