Polls v results: our track record

After each election we set our final poll average beside the result, party by party, and leave it here. Misses stay on the page.

Mean miss: average absolute difference between our final poll average and the result, over the named parties, in points. Each page gives the polls used, their dates and the source of the result. How the averages are made.

• The polls. The last Sondagio average before the vote. Each election's page lists the pollsters that went into it and the date of the last fieldwork.
• The result. The official count, with its source and the day it was read. A page says "provisional" until the official result is declared, then "final".
• Seats. Where we published a seat projection, the seats projected are set beside the seats won, party by party.
• Frozen. The comparison is a copy taken after the vote. Later corrections to the poll files do not change it, so a miss cannot be tidied away.
• Timing. An election is added once its count has stopped moving, not on election night.

A poll average is not a forecast: it says where the published polls stood, and each poll carries a margin of error of about 2 to 3 points. This page shows how far that was from the vote.