It is aaylws useful to look at the detailed data in these polls . Looking at the Mori poll , the raw data is 136 people voting LibDem now compared to 106 ( both figures out of 1004 ) who voted LibDem in 2005 . Mori do not weight for past vote but ICM weight to a past vote figure of 13% . ICM would therefore automatically have weighted up the 136 figure to circa 155 and a headline LibDem figure of around 19-20 % . What evidence do we have that the ICM approach is more likely correct than Mori ? We can again find some from the detailed Mori data . They find 30 people who voted Labour in 2005 now saying they will vote LibDem and just 6 who voted LibDem saying they will now vote Labour . They similarly find 15 switchers from LibDem to Conservative with 7 in the reverse direction . It is not possible to deduce the interchanges with Others . Clearly these figures indicate a much better performance for the LibDems compared to 2005 than the Mori published figures for this poll of 17% or just 14% on their absolutely certain to vote figure .

by Yun 10:39:22 AM 2012.02.26