Track Record

This page first posted 2 May 1997

The uniform national swing algorithm has been used here to predict general elections since 1992. Here is the record of those predictions, shown against what actually happened.

April 1992 Election

Prediction: Labour 17 seats short of a majority
Actual result: Conservative majority of 20

PartyPred VotesPred Seats  Actual VotesActual Seats
CON36.9%295 42.8%335
LAB39.0%308 35.2%271
LIB19.8%20 18.3%20

Electoral Calculus got 1992 spectactularly wrong. We predicted a Labour victory, but with a hung parliament. In fact the Conservatives were returned to office with a reduced majority. The principal cause of the error was that the opinion polls mis-estimated the relative support of the two parties.

Polls' error: 9.5% to Labour

The polls gave Labour a 2% lead, when actually the Conservatives were 7.5% ahead. That error of 9% was later ascribed to a combination of "shy Tories" declining pollster's questions; a late swing away from Labour; and errors in reweighting samples to match national averages.

The pollsters took the 1992 debacle very seriously, and put much effort into improving their methods. This would pay off next time, but they had already lost credibility.

May 1997 Election

Prediction: Labour majority of 171
Actual result: Labour majority of 179

PartyPred VotesPred Seats  Actual VotesActual Seats
CON30.6%191 31.4%165
LAB47.2%415 44.4%419
LIB15.4%25 17.2%46

This year, the pollsters were true Cassandras - they predicted gloom for the Conservatives, but were not fully believed. Many remembered the errors of 1992 and were unconvinced by the polling figures. However they turned out to be broadly accurate, and Labour did indeed win a landslide majority. On election night, Martin Baxter was the first commentator on the BBC to correctly predict the scale of their victory.

Poll's error: 3.5% to Labour

The polls were very successful this year in predicting that Labour would win a landslide. But there still seemed to be a bias towards Labour, although much less than previously.

June 2001 Election

Prediction: Labour majority of 211
Actual result: Labour majority of 167

PartyPred VotesPred Seats  Actual VotesActual Seats
CON30.3%150 32.7%166
LAB46.3%435 42.0%413
LIB17.5%45 18.8%52

In 2001, although the polls exaggerated Labour's lead, the result was largely unchanged from the previous election. Since the polls overestimated Labour's lead by over 6%, the actual majority would have been around 147 on a uniform swing basis. The non-uniform swing in some marginal seats makes the prediction seem less inaccurate than it deserves. Full details of 2001 errors.

Polls' error: 6.5% to Labour

The polls did accurately predict another Labour landslide. But again their exact numbers overstated Labour's lead somewhat. You can see the final 2001 Opinion polls.

May 2005 Election

Prediction: Labour majority of 132
Actual result: Labour majority of 66

PartyPred VotesPred Seats  Actual VotesActual Seats
CON31.7%170 33.2%198
LAB37.5%389 36.2%356
LIB22.8%58 22.6%62

In 2005, the poll and model errors did not cancel out but both pushed in the same direction. The polls' error, although smaller, still exaggerated the predicted Labour majority. Also regional swings, some tactical voting unwind and other non-linear effects further reduced the actual majority.
Full details of 2005 errors.

Polls' error: 2.9% to Labour

The pollsters were more accurate than in previous years, but there was still a small pro-Labour bias. Interestingly, the new organisation YouGov which uses internet polling had the most accurate results. You can see the final 2005 Opinion polls.

Next Time

The future is uncertain. The two caveats to bear in mind when using the election prediction are: If you wish to make your own adjustments to the published polls, you can easily translate that into seats using the user-defined prediction.