Data sources

Where the numbers come from

General elections 1918–2005: General election results from 1918 to 2019 (House of Commons Library, CBP-8647). This dataset gives, for every constituency, the electorate, the votes cast and the votes for each party. It does not name candidates, so pages for these elections show results by party. We used the tidy version published by Andy Medcalf (amedcalf/dabbling_with_data) and the version with seat counts and boundary sets published by Rhys Wheater (RhysWheater/election-analysis), which also includes the university seats.

General elections 2010–2024 and by-elections from 2010: UK Parliament’s election results database (electionresults.parliament.uk, compiled with the House of Commons Library and Democracy Club), which names every candidate, their party, whether they were a sitting MP, and the declared result. The 2024 page compares each constituency with the Library’s notional 2019 results on the new boundaries. We used the copy of this database published with fsargent/electionresults.uk.

Contains Parliamentary information licensed under the Open Parliament Licence v3.0.

Two-member and university seats (1918–1945)

Until 1950 a few towns and the universities elected two or three MPs. For those seats the Library dataset gives votes by party, not by candidate, so we cannot say which parties won the seats unless they were unopposed. National seat totals for 1918–1945 on this site therefore cover single-member and unopposed seats only, and each election page says how many seats are not allocated. The election pages also show the Library’s own published Conservative and Labour seat totals for comparison.

Party labels

The 1918–2019 dataset groups the Scottish National Party and Plaid Cymru together in some years; we show them as SNP in Scotland and Plaid Cymru in Wales. Before 1974 the Ulster Unionists are counted with the Conservatives, as in the source. “Others” in elections before 2010 combines all smaller parties and independents (including the Speaker in most years).

Party leaders and governments

The leaders of the main parties at each election and the government formed afterwards are well-documented historical facts that we have entered by hand.

Maps

Hexagon maps: Open Innovations hexmaps (MIT licence). Constituency, nation and region outlines: Office for National Statistics, Westminster Parliamentary Constituencies (July 2024) ultra-generalised boundaries, via horankev/voteReproject. Contains OS data © Crown copyright and database right; source: Office for National Statistics licensed under the Open Government Licence v3.0.

Portraits

MP portraits, where shown, are loaded from the UK Parliament Members API and are licensed under the Open Parliament Licence v3.0.

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