The methodological briefing below sets out the results of the 2015 review of the primary urban area (PUA) definition of cities. The results of this review will be used as the base unit of analysis for Centre for Cities’ work from 2016 onward, starting with Cities Outlook 2016.
From an economic point of view, a city is the concentration of a large amount of economic activity in a relatively small area. The best performing cities make the most of this density so that the value of what they produce is greater than the value of the inputs (workers, land etc.) that they use to produce it. This process is known as agglomeration.
Given that the mission of the Centre for Cities is to look at the economies of UK cities, it is the economic concentration perspective of the city that we are most interested in. This means that we require a definition that best matches this requirement. A number of different approaches could be used. But by defining cities principally on their built-up area – that is, the physical footprint of a city – the PUA definition is, in our view, the best option.
We have worked with the academics at CURDS, University of Newcastle to update the PUA definition and refine the methodology. We did this in three main ways:
This has lead to the following changes in the list of cities we analyse: