The 2019 General Election has delivered a sizeable majority for Boris Johnson’s Conservatives.

The Tories got 43.6 per cent of all votes cast – but 56 per cent of all the seats in the House of Commons.

This has sparked debate on social media about whether the system Britain currently uses to elect MPs – “First Past the Post” – is fair.

Under First Past the Post, the candidate with the most votes wins the seat, even if lots of votes are cast for other parties.

Supporters say the system is easy to understand and often produces decisive majorities for the bigger parties.

Opponents say this leads to a lot of “wasted” votes, and some strange outcomes when you look at the results across the country.

What would the results look like under PR?

It’s impossible to say for sure, as there are lots of different systems of counting votes proportionally, and people’s voting behaviour would almost certainly change under a different system.

Nevertheless, we can get an idea of how different this election might have been by working out how the shares of the popular vote won by each party would have translated into seats. We’ve used the modified D’Hondt method, one popular variation of PR:

One headline is that while the Conservatives would still have the lead in terms of seats, Labour could conceivably have formed a coalition government with other parties who promised to hold a second Brexit referendum.

Parties who either wanted to cancel Brexit or offer voters another referendum on EU withdrawal (Labour, Lib Dems, SNP, Green, Plaid Cymru) collectively won 51 per cent of the votes yesterday.

The parties who supported some form of Brexit – the Conservatives, the DUP and the Brexit Party – got about 46 per cent. But of course, Brexit looks likely to be the outcome of this election.

How did individual parties fare?

The Liberal Democrats would have more than 70 parliamentary seats to show for their 3.7 million votes under this form of PR, instead of the 11 they really bagged.

In fact, under First Past the Post, the Lib Dems actually saw their number of MPs drop by one, despite increasing their share of the popular vote by more than 4 percentage points.

The Greens might feel aggrieved too. They got more votes than Sinn Fein, the DUP, the SDLP and the Alliance party put together, but only have one MP to show for it, compared to the 18 seats those Northern Irish parties have between them.

Were Labour robbed by First Past the Post?

Not really. The share of the vote won by Labour (32.2 per cent) in this election almost exactly matches the share of seats they won (31.2 per cent).

Historically, Labour have benefited from First Past the Post. This is the first election since 1959 when Labour’s share of the popular vote was not greater than the percentage of seats won:

When Tony Blair won a landslide victory in 1997, he got almost exactly the same share of the popular vote that Boris Johnson did yesterday – just over 43 per cent.

But in 1997, the same vote share translated into 418 seats for Labour – more than 50 more seats than the Conservatives have now.