This month the Boundary Commissions for England, Wales, and Northern Ireland announced their initial proposals for new Parliamentary constituencies under the 2018 Boundary Review. (The Boundary Commission for Scotland is expected to publish their initial proposals on the 20th of October.)

We’ve created an online tool to analyse boundary changes

To help understand the impact of these proposed changes, we built a small web-app that allows you to compare the current and proposed constituencies, along with the wards that make them up. Constituency Boundaries is a tool that shows all three sets of boundaries on the same map, and provides easily accessible information about the electorates in each area.

It works like a layer-cake

The three sets of boundaries are stacked top to bottom, and information about the areas in the topmost layer is shown in the Area Information control at the bottom right of the map.

This happens when you mouse over an area on a desktop computer, or when you press and hold on an area with your finger on a touchscreen device. By default wards are the topmost layer, but each of the layers can be brought to the top by toggling it using the checkboxes.

And allows users to build their own constituencies

Ward areas are special in that you can select a set of wards by clicking on them and the combined electorate of all of the selected wards is shown in the Electorate box at the top right. You can download the names, codes, and electorates of the selected wards by clicking Get Data.

It provides data on the size of the electorate by ward

The tool has been designed to meet two specific needs.

We want to be able to easily explore the impact on the electorate of adding and removing particular wards from a constituency, and we want to be able to build up demographic profiles of proposed constituencies by linking wards to Census data.

And is openly available to all online

The tool was built principally to meet our needs here in the Commons Library, and it may change over time as these needs evolve, but we are making it openly available on the web to help the wider public engage with the 2018 Boundary Review.

The House of Commons Library Constituency Boundaries tool is available online from http://constituencyboundaries project management