Changing boundaries shouldn’t change election results

Doug Cowan, Head of Digital

Posted on the 16th January 2024

For the past 30 years, political scientists Colin Rallings and Michael Thrasher have been investigating how new boundaries will impact the political makeup of Parliament. Whenever new constituency maps are designed, they estimate what the current parliament would have looked like under the new seats, to create ‘notional’ results for 2019. These figures will be used by the main broadcasters in the upcoming general election so they can say whether a party’s vote has gone up or down in a seat, or whether it has changed hands.

They published their latest findings today, which can be explored in detail online. One of the main headlines is that, had 2019’s general election been fought under the new constituency map, the Conservative Party would have won 7 more seats, Labour lost 2, the Liberal Democrats lost 3 and Plaid Cymru would have lost 2.

Who wins and loses can change without a single voter changing their mind

While there has been plenty of discussion of the notional results and what they mean, there has not nearly been enough discussion on how ridiculous it is that the results would have been different with a different constituency map. Shouldn’t MPs win or lose their seats based on voters changing their minds? Yet here we have MPs who would have lost their seats purely due to where a civil servant drew a line on a map.

Voters looking forward to holding their MP to account will suddenly find they have been moved to a neighbouring constituency, with an entirely different MP.

Thankfully, the UK’s independent Boundary Commissions have not done this on purpose. They run an open process, with public feedback at each stage. It’s a depressingly inevitable result of Westminster’s First Past the Post system.

In theory, you could design hundreds of different constituency maps that would all result in a different makeup of Parliament. Where the lines go can directly change who represents you in Parliament, and how many MPs each party has. Which one of these results is the fair one?

Constituency Example
Here is a fictional town. As the constituency borders rotate around, control of the town council swings between the parties, but no voters change their votes.

The Boundary Commissions have a few rules when designing their maps. They can only vary by +/-5% in size, no seats can cross national borders, seats must be smaller than 13,000 square km and the Commissions can only consider geographical considerations, local government boundaries, boundaries of existing constituencies and local ties or the inconveniences attendant on such changes (there are special rules for various islands).

What they can’t do is try to make parliament representative of political opinion in the country. Which of course is right, as political opinion changes quickly, but if an electoral system can’t create a parliament that is responsive to public opinion shouldn’t we accept that the system needs changing?

An inevitable result of Westminster’s First Past the Post system

The First Past the Post electoral system in Westminster is simply not designed to distribute seats in line with the actual share of the vote given to each party.

The problem stems from the fact that each constituency elects only one Member of Parliament, and there is no set amount of support they need to win to get elected. While some MPs amass substantial majorities, others manage to win by mere handfuls of votes. The surplus votes garnered by landslide victories contribute little to the overall composition of parliament.

Beyond the traditional Labour versus Conservative dynamic, the presence of third parties, even if they don’t emerge victorious, can significantly impact the electoral landscape. The Liberal Democrats, Green Party and Reform UK might all draw substantial shares of the vote, in effect lowering the threshold for a major party to secure a seat.

One MP could be elected with 70% of the vote and another on 35%. If the MP on 70% sees their constituency re-drawn and they lose a village that used to support them to a neighbour, while gaining an area that doesn’t like them, they will simply win on 65% next time. For the MP elected on 35% the same thing could happen, and it could result in them losing their seat.

We need an electoral system designed to represent voters

A solution to this problem lies in embracing electoral systems designed to make a parliament that represents voters, such as the Single Transferable Vote.

Rather than dividing our towns and counties up arbitrarily into single-MP constituencies, we could keep them together and let the whole area elect a group of MPs. This group of MPs would represent the political diversity of the area. The same number of MPs and voters, just elected from one big area rather than lots of small ones. When populations increase or decrease, the boundaries can stay the same but the number of MPs elected can change.

Rallings and Thrasher’s work shows Westminster’s inherently chaotic system operating exactly as anticipated. We need to throw out the First Past the Post system and adopt an electoral system designed to make every vote count.

Do you agree? Add your name to our call for proportional representation for Westminster

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