Tonight’s Newsnight features a discussion of the electoral system — and in particular the number of seats each party can expect to win, supposing it wins a particular share of the vote.
This calculation can be represented visually using a seats-votes curve.
The particular seats votes curves shown tonight are based on the forecasts produced by electionforecast.co.uk.
Because these forecasts are made by simulating lots of elections, we can start record the average number of seats won in all those simulations where a party won 30% of the vote, or 35%, or 3% of the vote, and so on. (Actually, it’s a bit more complicated than that, and used some non-parametric regression, but we’ll ignore that).
Because those forecasts change daily, the seats-votes curves change daily. But you can find a simplified version of the seats votes curve shown on tonight’s show in this Excel file.
There are two things to note:
- we only show expected seats for vote shares which featured in the simulation (so there are no predictions for the Conservative seat tally with 1% of the vote), and
- the best source of predictions remains the main electionforecast.co.uk site