The 2015 election results were a disaster for the polling companies, who drastically underestimated the Conservative vote and predicted an almost entirely different outcome to what happened on the night. Therefore when I made my predictions on the election results, I too was fooled by false illusions of what was to be. So blame them not me!
But although my vote share predictions were off, and so were my final seat predictions, as it happens my model for each constituency managed to hold up and predict 89% of seats correctly. While from a statistical standpoint and from the final result it does not mean my predictions were a success, it certainly shows that there was definitely a decent level of accuracy at play.
Here is the breakdown of how my predictions went on the night:
| Correct | Wrong | % | |
| England | 470 | 63 | 88% |
| Scotland | 53 | 6 | 90% |
| Wales | 38 | 2 | 95% |
| N. Ireland | 15 | 3 | 83% |
| Total | 576 | 74 | 89% |
| Correct | Wrong | % | |
| Certain | 329 | 6 | 98% |
| High Likely | 81 | 1 | 99% |
| Likely | 74 | 7 | 91% |
| Leaning | 53 | 30 | 64% |
| TCTC | 39 | 30 | 57% |
| Total | 576 | 74 | 89% |
These show generally that in the seats where I was predicting to make Labour gains the swing towards them did not materialise. The major wrong answers in the Certain, High Likely and Likely columns are mostly Lib Dem defeats – with the polls coming nowhere near to showing the catastrophe that would befall them in some of their safest seats.
For the 2020 election things will be much easier, at least if the current state of the parties stays roughly similar. Assuming there is no rise of a new party, like we had with UKIP this year, uniform swing will once again work – allowing us to accurately model where party support will rise and fall in individual constituencies.
So here is a full breakdown of where things went wrong in my predictions, and also where seats changed hands (as all other constituency predictions were correct and resulted in no overall impact on the election result):
| Prediction | Winner | Gain? | Correct | Certainty | |
| Aberdeen North | SNP | SNP | Gain | Yes | Certain |
| Aberdeen South | SNP | SNP | Gain | Yes | High Likely |
| Aberdeenshire West & Kincardine | SNP | SNP | Gain | Yes | Certain |
| Airdrie & Shotts | SNP | SNP | Gain | Yes | Likely |
| Antrim South | DUP | UUP | Gain | No | Leaning |
| Argyll & Bute | SNP | SNP | Gain | Yes | Certain |
| Ayr, Carrick & Cumnock | SNP | SNP | Gain | Yes | Likely |
| Ayrshire Central | SNP | SNP | Gain | Yes | Likely |
| Ayrshire North & Arran | SNP | SNP | Gain | Yes | Certain |
| Bath | LibDem | Con | Gain | No | Likely |
| Bedford | Lab | Con | No | Leaning | |
| Belfast East | DUP | DUP | Gain | Yes | Leaning |
| Bermondsey & Old Southwark | Lab | Lab | Gain | Yes | TCTC |
| Berwickshire, Roxburgh & Selkirk | LibDem | SNP | Gain | No | Leaning |
| Berwick-upon-Tweed | Con | Con | Gain | Yes | TCTC |
| Birmingham Yardley | LibDem | Lab | Gain | No | TCTC |
| Bolton West | Lab | Con | Gain | No | Leaning |
| Bradford East | Lab | Lab | Gain | Yes | High Likely |
| Bradford West | Other | Lab | Gain | No | Certain |
| Brecon & Radnorshire | Con | Con | Gain | Yes | TCTC |
| Brent Central | Lab | Lab | Gain | Yes | High Likely |
| Brentford & Isleworth | Lab | Lab | Gain | Yes | Leaning |
| Brighton Kemptown | Lab | Con | No | Leaning | |
| Bristol West | Lab | Lab | Gain | Yes | High Likely |
| Broxtowe | Lab | Con | No | Leaning | |
| Burnley | Lab | Lab | Gain | Yes | High Likely |
| Bury North | Lab | Con | No | TCTC | |
| Caithness, Sutherland & Easter Ross | SNP | SNP | Gain | Yes | High Likely |
| Cambridge | LibDem | Lab | Gain | No | TCTC |
| Cannock Chase | Lab | Con | No | Leaning | |
| Cardiff Central | Lab | Lab | Gain | Yes | TCTC |
| Cardiff North | Lab | Lab | Gain | Yes | TCTC |
| Carlisle | Lab | Con | No | Leaning | |
| Cheadle | LibDem | Con | Gain | No | Leaning |
| Cheltenham | Con | Con | Gain | Yes | TCTC |
| Chester, City of | Lab | Lab | Gain | Yes | Leaning |
| Chippenham | Con | Con | Gain | Yes | Likely |
| Coatbridge, Chryston & Bellshill | SNP | SNP | Gain | Yes | Likely |
| Colchester | LibDem | Con | Gain | No | TCTC |
| Corby | Lab | Con | Gain | No | Certain |
| Cornwall North | LibDem | Con | Gain | No | Leaning |
| Crewe & Nantwich | Lab | Con | No | TCTC | |
| Cumbernauld, Kilsyth & Kirkintilloch East | SNP | SNP | Gain | Yes | Certain |
| Derby North | Lab | Con | Gain | No | Likely |
| Devon North | Con | Con | Gain | Yes | Certain |
| Dewsbury | Lab | Lab | Gain | Yes | Leaning |
| Dorset Mid & Poole North | Con | Con | Gain | Yes | Likely |
| Down North | UUP | Other | Gain | No | Certain |
| Dumfries & Galloway | SNP | SNP | Gain | Yes | Likely |
| Dumfriesshire, Clydesdale & Tweeddale | SNP | Con | No | Likely | |
| Dunbartonshire East | SNP | SNP | Gain | Yes | TCTC |
| Dunbartonshire West | SNP | SNP | Gain | Yes | High Likely |
| Dundee West | SNP | SNP | Gain | Yes | Certain |
| Dunfermline & Fife West | SNP | SNP | Gain | Yes | Leaning |
| Ealing Central & Acton | Lab | Lab | Gain | Yes | TCTC |
| East Kilbride, Strathaven & Lesmahagow | SNP | SNP | Gain | Yes | High Likely |
| East Lothian | SNP | SNP | Gain | Yes | Likely |
| Eastbourne | LibDem | Con | Gain | No | Certain |
| Eastleigh | LibDem | Con | Gain | No | High Likely |
| Edinburgh East | SNP | SNP | Gain | Yes | High Likely |
| Edinburgh North & Leith | SNP | SNP | Gain | Yes | Likely |
| Edinburgh South | SNP | Lab | No | TCTC | |
| Edinburgh South West | SNP | SNP | Gain | Yes | High Likely |
| Edinburgh West | SNP | SNP | Gain | Yes | High Likely |
| Elmet & Rothwell | Lab | Con | No | TCTC | |
| Enfield North | Lab | Lab | Gain | Yes | Leaning |
| Erewash | Lab | Con | No | TCTC | |
| Falkirk | SNP | SNP | Gain | Yes | Certain |
| Fermanagh & South Tyrone | Sinn Fein | UUP | Gain | No | Certain |
| Fife North East | SNP | SNP | Gain | Yes | TCTC |
| Finchley & Golders Green | Lab | Con | No | TCTC | |
| Glasgow Central | SNP | SNP | Gain | Yes | Likely |
| Glasgow East | SNP | SNP | Gain | Yes | High Likely |
| Glasgow North | SNP | SNP | Gain | Yes | Likely |
| Glasgow North East | Lab | SNP | Gain | No | TCTC |
| Glasgow North West | SNP | SNP | Gain | Yes | Likely |
| Glasgow South | SNP | SNP | Gain | Yes | Certain |
| Glasgow South West | SNP | SNP | Gain | Yes | High Likely |
| Glenrothes | SNP | SNP | Gain | Yes | TCTC |
| Gordon | SNP | SNP | Gain | Yes | Likely |
| Gower | Lab | Con | Gain | No | Leaning |
| Halesowen & Rowley Regis | Lab | Con | No | TCTC | |
| Harrow East | Lab | Con | No | TCTC | |
| Hastings & Rye | Lab | Con | No | Leaning | |
| Hazel Grove | LibDem | Con | Gain | No | TCTC |
| Hendon | Lab | Con | No | Leaning | |
| Heywood & Middleton | UKIP | Lab | No | TCTC | |
| Hornsey & Wood Green | Lab | Lab | Gain | Yes | Leaning |
| Hove | Lab | Lab | Gain | Yes | Leaning |
| Ilford North | Con | Lab | Gain | No | TCTC |
| Inverclyde | SNP | SNP | Gain | Yes | Certain |
| Inverness, Nairn, Badenoch & Strathspey | SNP | SNP | Gain | Yes | Certain |
| Ipswich | Lab | Con | No | Leaning | |
| Keighley | Lab | Con | No | TCTC | |
| Kilmarnock & Loudoun | SNP | SNP | Gain | Yes | High Likely |
| Kingston & Surbiton | LibDem | Con | Gain | No | Leaning |
| Kirkcaldy & Cowdenbeath | SNP | SNP | Gain | Yes | Likely |
| Lanark & Hamilton East | SNP | SNP | Gain | Yes | Likely |
| Lancaster & Fleetwood | Lab | Lab | Gain | Yes | Leaning |
| Lewes | LibDem | Con | Gain | No | Leaning |
| Lincoln | Lab | Con | No | Leaning | |
| Linlithgow & Falkirk East | SNP | SNP | Gain | Yes | High Likely |
| Livingston | SNP | SNP | Gain | Yes | Certain |
| Manchester Withington | Lab | Lab | Gain | Yes | High Likely |
| Midlothian | SNP | SNP | Gain | Yes | High Likely |
| Milton Keynes South | Lab | Con | No | TCTC | |
| Morecambe & Lunesdale | Lab | Con | No | Leaning | |
| Morley & Outwood | Lab | Con | Gain | No | Likely |
| Motherwell & Wishaw | SNP | SNP | Gain | Yes | High Likely |
| Northampton North | Lab | Con | No | TCTC | |
| Norwich North | Lab | Con | No | TCTC | |
| Norwich South | Lab | Lab | Gain | Yes | Likely |
| Nuneaton | Lab | Con | No | TCTC | |
| Ochil & South Perthshire | SNP | SNP | Gain | Yes | Certain |
| Paisley & Renfrewshire North | SNP | SNP | Gain | Yes | Leaning |
| Paisley & Renfrewshire South | SNP | SNP | Gain | Yes | Likely |
| Peterborough | Lab | Con | No | TCTC | |
| Plymouth Moor View | Lab | Con | Gain | No | Likely |
| Plymouth Sutton & Devonport | Lab | Con | No | Leaning | |
| Portsmouth South | Con | Con | Gain | Yes | Likely |
| Pudsey | Lab | Con | No | TCTC | |
| Redcar | Lab | Lab | Gain | Yes | Certain |
| Renfrewshire East | Lab | SNP | Gain | No | TCTC |
| Rochester & Strood | Con | Con | Gain | Yes | TCTC |
| Ross, Skye & Lochaber | SNP | SNP | Gain | Yes | Leaning |
| Rutherglen & Hamilton West | Lab | SNP | Gain | No | TCTC |
| Sherwood | Lab | Con | No | Leaning | |
| Solihull | Con | Con | Gain | Yes | Likely |
| Somerton & Frome | Con | Con | Gain | Yes | Leaning |
| Southampton Itchen | Lab | Con | Gain | No | Leaning |
| St Austell & Newquay | Con | Con | Gain | Yes | Likely |
| St Ives | Con | Con | Gain | Yes | Leaning |
| Stevenage | Lab | Con | No | TCTC | |
| Stirling | SNP | SNP | Gain | Yes | Certain |
| Stockton South | Lab | Con | No | TCTC | |
| Stourbridge | Lab | Con | No | TCTC | |
| Stroud | Lab | Con | No | Leaning | |
| Sutton & Cheam | Con | Con | Gain | Yes | Leaning |
| Swindon South | Lab | Con | No | TCTC | |
| Taunton Deane | Con | Con | Gain | Yes | TCTC |
| Telford | Lab | Con | Gain | No | Likely |
| Thornbury & Yate | LibDem | Con | Gain | No | Certain |
| Thurrock | UKIP | Con | No | TCTC | |
| Torbay | LibDem | Con | Gain | No | TCTC |
| Twickenham | LibDem | Con | Gain | No | Leaning |
| Vale of Clwyd | Lab | Con | Gain | No | Leaning |
| Warrington South | Lab | Con | No | Leaning | |
| Warwickshire North | Lab | Con | No | Leaning | |
| Waveney | Lab | Con | No | Leaning | |
| Weaver Vale | Lab | Con | No | Leaning | |
| Wells | Con | Con | Gain | Yes | Likely |
| Wirral West | Lab | Lab | Gain | Yes | Leaning |
| Wolverhampton South West | Lab | Con | No | Leaning | |
| Wythenshawe & Sale East | UKIP | Lab | No | Leaning | |
| Yeovil | LibDem | Con | Gain | No | Likely |