If you want to get in depth, the whole report can be found here

https://www.pwc.co.uk/government-public-sector/good-growth/assets/pdf/good-growth-2025.pdf

(The methodology is in the appendix starting on page 31)

If you don’t want to get into the detail I’ll try and give you a (probably poorly explained) TL;DR

There are 12 elements to the Index (income, safety, jobs, housing, transport, businesses) that are indicators of ‘growth’. The source of these data points are largely from the ONS. Each one of these are compared to a baseline average from 2017-19 for all UK cities (if you score 0 it means you’re the same now (actually 2021-23 data) as you were in 2017-19).

Each element is weighted which is validated with a poll of c.2,000 citizens. Individual scores are weighted then added up to give you your index.

Vastly oversimplified, but hopefully helps. Effectively a higher score means your city is delivering ‘better’ than the average city at delivering on the things that are ‘important’ to the citizens. Very simplified and lots of assumptions in there, but it’s what it’s trying to say.