Vote 2010: today's election barometer
Updated on 14 April 2010
The Conservative poll lead narrows, but can the Tories still win an overall majority? Professor Leighton Vaughan Williams of Nottingham Business School's Political Forecasting Unit, examines the evidence.
Taken as a whole, the latest polls show a narrowing of the Conservative poll lead, though the broad picture remains little changed, i.e. a Conservative percentage vote share toward the upper 30s, Labour in the lower 30s and the Liberal Democrats at or around 20 per cent.
The markets continue to point to a small Tory majority, albeit down now to only 8 seats, compared to 10 yesterday and over 20 a few days ago. The Political Forecasting Unit 'Polling Tracker' has the Conservatives six points ahead of Labour.
Reproduced as a uniform swing across the country, this would put both the Conservatives and Labour on 283 seats, which would make the projected 53 seats for the Liberal Democrats critical to securing a majority in the House of Commons.
Polling Commentary
There are four national polls out today.
Angus Reid/Political Betting: Con 38, Lab 28, LD 22
ComRes/ITV/Independent: Con 36, Lab 31, LD 19
Populus/Times: Con 36, Lab 33, LD 21
YouGov/Sun: Con 39, Lab 31, LD 20
In terms of a headline poll lead, these findings are extremely divergent, ranging from a Conservative lead over Labour of as much as 10 points with Angus Reid but only 3 points with Populus.
As a measure of each party's individual standing, however, there is much greater correspondence. All four polls have the Conservatives within 1.5 points of 37, Labour within 2.5 points of 30.5 and the Liberal Democrats within 1.5 points of 20.5.
Why the difference?
Partly it may be the way that the different polling organisations conduct their polling. Angus Reid and YouGov, for example, conduct their surveys online, whereas ComRes and Populus conduct interviews by telephone. Partly it is sampling error, i.e. no single sample of the population is likely to mirror exactly the whole population.
The various polling organisations thus adjust the raw data to allow for differences in the demographic mix of the sample compared to the total adult population. Allowance also has to be made for the likelihood that a member of the sample will actually vote.
The different polling organisations make these adjustments in different ways, however, which can also be a source of divergence. In addition, fieldwork for different polls may be conducted at different times.
Today, for example, the Populus and YouGov results are generated from fieldwork undertaken on 12 and 13 April, while Angus Reid and ComRes conducted their surveys on 11 and 12 April. These are all important and interesting issues, which I shall consider further as the election progresses.
Political Forecasting Unit's (PFU) "polling tracker" has the Conservatives down one since yesterday.
Put simply, the tracker is based on the most recent surveys by different polling organisations, and is adjusted so that the more recent the survey the more weight is attached to the vote shares. There is also some statistical smoothing which has the effect that outliers or vote shares that diverge most from the general consensus are allocated less weight.
Election barometer
The Political Forecasting Unit's 'election barometer', designed to capture the changing state of the race as it unfolds through the campaign, shows the Conservatives falling short of an overall majority based on the recent polling, assuming a uniform national swing.
But an analysis of the money bet in political betting markets currently translates into a Conservative overall majority of eight, and a 56.6 per cent chance of a Tory overall majority, down from 10 and 57.3 per cent yesterday.
Daily poll of polls
Conservative: 37 per cent
Labour: 31 per cent
Liberal Democrat: 21 per cent
PFU polling tracker (recent polls, weighted)
Conservative: 37 per cent
Labour: 31 per cent
Liberal Democrat: 20 per cent
Outcome (Based on polling tracker, assuming national swing reproduced in every constituency)
Conservatives: 283 seats
Labour: 283 seats
Liberal Democrat: 53 seats
Other: 31 seats
Conservatives and Labour short of an overall majority by 43.
Where the money is (Analysis based on money wagered on the election in political betting markets)
Conservative: 329 seats
Labour: 226 seats
Liberal Democrat: 62 seats
Translates into a Conservative overall majority of 8
(Chances based on odds from betting exchanges)
% chance of Conservative overall majority: 56.6 per cent
% chance of No overall majority: 36.9 per cent
% chance of Labour overall majority: 6.3 per cent
Professor Leighton Vaughan Williams is Director of the Political Forecasting Unit at Nottingham Business School.
