We am very grateful for comments from and discussions with various people on various aspects of our forecasting methodology including (in alphabetical order): Richard Coggins, Andrew Cooper, Philip Cowley, David Cowling, John Curtice, Rob Ford, Matt Goodwin, Chris Hanretty, Will Jennings, Ron Jonston, Jouni Kuha, Ben Lauderdale, Matt Lebo, Iain McLean, Jon Mellon, Andreas Murr, Clive Payne, Mark Pickup, Chris Prosser, Petra Schleiter, Mike Smithson, Jon Tonge, Nick Vivyan, Anthony Wells, Chris Wlezien and Chris Zorn.

We have also much appreciated the numerous and wide ranging comments on Twitter and elsewhere online. Our thinking has been informed and approach influenced by all the feedback.

The methodology for the forecast GB share of the vote for the three main British Westminster parties is set out in Fisher (2014). The ungated working paper version is here. That work in turn built on work in Fisher et al (2011), which in turn relied heavily on models set out in Wlezien and Erikson (2002).

The new simulation method has been influenced by discussions with the electionforecast.co.uk team but there are numerous differences in model specification and the approach here is primarily simulation and not Bayesian.

We are grateful to Joe Twyman for access to individual-level YouGov data,  Ben Lauderdale, Tom Lubbock and Eilidh Macfarlane for spreadsheets with Ashcroft constituency poll data,  Will Jennings for compiling and preparing the historical polling data, including interpolation and correction for overlaps, as used in Wlezien et al (2013), and ultimately to those who compile opinion polls and make them easily and quickly available online.

References

Fisher, Stephen D. 2014. “Predictable and Unpredictable Changes in Party Support: A Method for Long-Range Daily Election Forecasting from Opinion Polls” Journal of Elections, Public Opinion & Parties: 1–22

Fisher, Stephen D, Robert Ford, Will Jennings, Mark Pickup and Christopher Wlezien. 2011. “From polls to votes to seats: Forecasting the 2010 British general election” Electoral Studies 30(2): 250–257

Wlezien, C, and RS Erikson. 2002. “The timeline of presidential election campaigns” The Journal of Politics 64(04): 969–993

Wlezien, Christopher, Will Jennings, Stephen D Fisher, Robert Ford and Mark Pickup. 2013. “Polls and the Vote in Britain” Political Studies 61(S1): 66–91