Notes: The forecast base was the 2010 General Election, although gains are compared with the current situation (April 2015). The forecasting was made using the new, enhanced, UK-Elect v9.4 method, on a separate regional basis for Scotland, Wales, London, and Great Britain, with many other factors taken into consideration, including the number of days until the election, by-election results, local constituency opinion polls, and the changes in the national poll percentages since the by-elections and constituency opinion polls. Incumbency support was enabled, and configured to take account of whether or not the incumbent was standing again or standing down, and they were standing again it also took into consideration whether they had won the seat for the first time at the preceding election. (This is because some academic studies have suggested that the incumbency effect is greater for first time winners.)
See UK Election Forecasting Theory, Techniques and Controversial Discussions and UK Election Forecasting - A detailed explanation of the techniques used by UK-Elect for more details of UK-Elect forecasting techniques.
UK-Elect v9.4 users will be able to reproduce the above forecast by doing a "Guided Forecast" and specifying the separate percentages for Scotland, Wales, London and the overall GB percentages. Note that the method used was the UK-Elect v9.4 method with all the default UK-Elect settings for that method enabled, but date-specific adjustments (adjusting the calculation target percentages depending on the number of days until the election) were used for this forecast.Results from Northern Ireland are based on those of the last election and included for completeness only.
Hung Parliament - Labour Lead (By 6) But Short By 48. SNP Forecast to have 48.
In the latest, detailed (top 3 parties in every constituency) UK-Elect forecast Labour are predicted to form the largest party by six seats, and the Scottish National Party is once more forecast to have the key role in deciding who will form the next UK government. Overall, the figure of 325 seats, the combined total for Labour + SNP MPs in this prediction, is just enough for an overall majority if the two parties can come to an agreement.
This is the second forecast made using the new, improved, UK-Elect v9.4 method which takes account of even more factors than previously. Among the inputs taken into consideration by this forecast were: national opinion polls, regional opinion polls (for Scotland, Wales and London), the candidates standing in each seat and whether they were the incumbent, and if so, whether they won that seat for the first time at the previous election, by-elections, constituency opinion polls by Lord Ashcroft (including those published on April 8th) and others (adjusted according to how many days ago the fieldwork was done), and the change in the regional and national polls since the poll fieldwork or by-election.
The UK-Elect "adjust target percentages for date" option was also set for this forecast, adjusting the percentages to represent what we currently expect to happen on May 7th, rather than just using the current poll percentages as a target. This option has the affect of adjusting the input opinion poll percentages to take account of what happened in many past elections as the date of the election approached - i.e. that the support levels for the parties returned part-way towards their previous totals. In current circumstances this favours the Liberal Democrats slightly and disadvantages UKIP and the SNP.
The GB percentages input for this forecast were Con 33.5%, Lab 33.5%, UKIP 13.5%, Lib Dem 9%, Green 5%. For Scotland the percentages used were SNP 45%, Lab 28%, Con 15%, Lib Dem 4%, UKIP 4%, Green 3%, for Wales the percentages used were Lab 40% Con 25%, UKIP 14%, Plaid Cymru 11%, Lib Dem 5%, Green 4%, and for London the percentages used were Lab 44%, Con 33%, UKIP 9%, Lib Dem 8%, Green 5% Other parties votes were not specifically set. Note that the final forecast percentages differ from the input percentages due to the methodology used (including adjusting for the number of days until the election) - e.g. the final UK target percentages used were Con 33.6%, Lab 33.2%, UKIP 12.9%, LD 9.8%, Green 4.8%.