Although, the joint BBC/ITV exit poll in 2005 correctly predicted the 66 seat majority for Labour, don’t expect it to be as accurate tonight.
Early rumours suggest that the Conservative party have attracted 39% of the overall vote which would give them an overall majority - but here are some reasons to be wary:
1) The experts have to work around duff information since there is no data on voting at individual polling stations. The national census is nine years out of date and local election ward returns are a flawed guide to voting patterns for a general election.
2) Only one in six voters refuse to respond to an exit poll.
3) Up to one in five votes will be cast by post so are not reflected in the exit poll. Around 12 per cent voted this way last time, and the proportion is rising.
4) The traditional swingometer may be obsolete as even if they get the vote share correct, there’s a good chance the seat prediction will be flawed.
1) The experts have to work around duff information since there is no data on voting at individual polling stations. The national census is nine years out of date and local election ward returns are a flawed guide to voting patterns for a general election.
2) Only one in six voters refuse to respond to an exit poll.
3) Up to one in five votes will be cast by post so are not reflected in the exit poll. Around 12 per cent voted this way last time, and the proportion is rising.
4) The traditional swingometer may be obsolete as even if they get the vote share correct, there’s a good chance the seat prediction will be flawed.
5) The exit polling sample barely covers Lib-Lab marginals. Because there is no data from on individual polling stations, the wonks calculate the change from the 2001 and 2005 exit polls. It covers around 120 polling stations. But there’s only data on three Lib-Lab marginals. That’s why the Lib Dem vote share prediction was too low in 2005. The problem will be even greater this year.
6) Boundary changes muck up what historic data is available as since 2001, many boundaries have been revised. Some polling stations in the sample have been split in half, so how do you calculate the change in voting? On top of that, people move, meaning many polling stations serving very different communities.
It’s a mad rush to manage the data and make a prediction It’s a Thursday. Most people vote after they’ve been to work. That gives the boffins very little time to make the calculations. They’re working to a 10pm deadline and data is still streaming through until 7pm.
6) Boundary changes muck up what historic data is available as since 2001, many boundaries have been revised. Some polling stations in the sample have been split in half, so how do you calculate the change in voting? On top of that, people move, meaning many polling stations serving very different communities.
It’s a mad rush to manage the data and make a prediction It’s a Thursday. Most people vote after they’ve been to work. That gives the boffins very little time to make the calculations. They’re working to a 10pm deadline and data is still streaming through until 7pm.
So while the exit poll is the first indication of the potential result, it should certainly not be trusted as the actual result.
