Poll Dancing: How accurate are the polls?

How accurate have UK opinion polls been in recent years? Are some polls more accurate than others? Are they getting more exact as the technology gets better? Can I make a pretty image out of these questions?

 

See if you can spot any patterns.

 

Visualisation for The Guardian

www.guardian.co.uk/news/datablog/2010/may/06/general-elec...

 

Data here

spreadsheets.google.com/ccc?key=0Aqe2P9sYhZ2ndGlaWDJQMVN2...

 

More visualisations here

www.informationisbeautiful.net

 

Done