New Senedd Election System

As many of you are aware, the Senedd is changing from an Additional Member System (AMS) to the D'Hondt system. The BBC have published the Boundary Commission's proposed constituencies here. 32 general election constituencies are proposed to be paired up and made into 16 Senedd constituencies which each return 6 representatives to the Senedd.

Since there are no official estimates of the 2021 election on these proposed boundaries, I have made an estimate of my own. Essentially, I have a made a list of all new constituencies, matched them to their general election counterparts, and then matched those general election constituencies to their estimated 2021 Senedd election counterparts.

For example, the new "Cardiff East and North" Senedd constituency consists of general election seats "Cardiff East" and "Cardiff North". "Cardiff East" consists of 2021 Senedd seats "Cardiff Central" and "Cardiff South and Penarth" and "Cardiff North" consists of 2021 Senedd seat "Cardiff North". I have made the assumption that Senedd seats which consist of multiple general election seats comprise of them equally which, although rather crude, at least gives us a starting point.

If anyone wants to take a crack at calculating their own estimates with a better methodology, send them my way, and I will be more than happy to use those instead.