This blog post is part of our Repowering Democracy series. This year we will be publishing a series of short pieces of writing from mySociety staff and guest writers who are thinking about how our democracy works and are at the frontlines of trying to improve it.

This week our senior researcher, Alex Parsons, shares data we’ve produced about new constituencies, and how we should steer the process of boundary reform towards making our politics easier to navigate.

The current set of parliamentary constituencies is being replaced for the next election. For some, the main effect is a name change, but for others the borders of constituencies will change substantially.

Boundary reviews are carried out by four separate organisations — one for each nation — who each set their own boundaries. This means that no-one officially produces a single dataset of all the new constituencies covering the whole UK.

That seems like a useful thing to have, so we’ve created it. We’ve made:

• A single Excel download and geopackage listing all 650 new constituencies.
• A series of population and overlap files between old constituencies, old LSOA (2011) and current local authorities (2023) and the new constituency.
• A postcode lookup (England, Wales, Scotland only) for postcodes to new constituencies.
• A new tab/csv download for 2025 constituencies in our:
  • Composite UK-wide Index of Multiple Deprivation
  • Composite UK-wide Rural Urban Classification (RUC)
• For Python developers, a function that uses this data to transform between old, new and local authority geographies. The same data could be used in a similar way in other languages
• UPDATE: MapIt now makes both current and future constituencies available through the API and online postcode lookup. Enter any postcode to see the new constituency.

This contains both the official GSS id, and a unique ID based on the three letter IDs for new constituencies created by Philip Brown and Alasdair Rae for their hexmap of the new constituencies. This is useful in some instances because the GSS codes are not unique to the new constituencies (some Scottish constituencies are unchanged).

Political equality means more than equal seats

There are 650 MPs in the UK Parliament, each is elected from a constituency, and each constituency only has one MP.

The main change in the new rules is reducing the tolerance for differences in the number of registered voters between constituencies, and ending the previous separate weighting of Wales. This means that some areas are affected much more than others by the change – with the number of Welsh seats reduced by eight, and Scotland losing two seats in total.

Boundary changes aren’t just a technical process, but have impacts on the results of elections. In the UK, politicians can’t directly draw boundaries, but this doesn’t mean they’re not a political choice. The boundary commissions follow the rules they are set, but what these rules are (and how often they happen) are the subject of political debate where everyone has one eye on the outcomes that different sets of rules produce. The debate about “equal size constituencies” versus boundaries that reflect “natural communities” is in part about different perceived partisan advantages of drawing lines in different ways.

Advocates of constituencies of equal size argue that this is about political equality. Now, we like political equality, but taking this argument seriously should lead you way past equal size to supporting a move to proportional representation. In practice, everyone in this debate accepts trade-offs between political equality and other factors. If we’re not going to have proportional representation, we think clear lines between different levels of government are features that should have real weight.

Effective and understandable layers of representation

We are in favour of layers of representation that are effective and easy to understand. Through postcode lookups on TheyWorkForYou and WriteToThem we can explain the overlaps for a user’s own postcode, but the simpler the system the easier it is for people to understand what is happening – whether or not they visit one of our websites.

When boundaries are less complex, it’s also easier for people working inside the system to understand how the pieces fit together. Tighter requirements on populations means more constituencies will cross local authority boundaries. Using our new datasets, we can say that the number of constituencies that have more than 5% of its population in at least one other local authority has increased from 26% to 38%.

This means there are an increasing number of MPs who have a harder job than others – working with different or multiple local authorities depending on the issue at hand. Knowledge and understanding of local systems is much more complicated for these MPs, and getting problems to the right place is more challenging for their staff.

Tighter requirements also mean more frequent changes. The current timetable will lead to this process being repeated every other election, disrupting understanding of constituencies and processes of accountability.

The reason we’ve produced this data in the first place is to help organisations we are working with transform information they have about current constituencies into information that is useful for new constituencies. Institutions inside and outside the formal political system develop an understanding of the country that is disrupted by changing boundaries.

This problem also applies to the understanding MPs have of their own area – both in terms of learned understanding, and statistics and reports created to inform them. Changing boundaries means everyone has to change their understanding of what a constituency looks like. This is all bad from the point of view of effective understanding and interrelation of layered government.

Something that should be key when designing our political system is making sure that it can be understood by citizens and representatives, and supports effective communication between layers of government.

If we designed our institutions and boundaries to be easily navigated, rather than meet mathematical rules, what would that look like? Certainly there should be better alignment between different layers of government, but can we go further than that? We want better postcode data so that we can fix the problems of when the same postcode is in multiple areas, but from a public understanding point of view – why shouldn’t the line drawers respect postcode boundaries in the first place? They’re a lot more real to people than the process that produces our boundaries now.

The way we draw our boundaries is part of wider arguments about the different priorities we have when we design political institutions – and the idea that things should be easy to understand and navigate is currently undervalued.

Image: Héctor J. Rivas on Unsplash.