In his northern powerhouse speech yesterday the Chancellor set out his proposals to create a ‘super city’ of the north by connecting the ribbon of cities stretching from Liverpool to Hull via Manchester, Leeds, Sheffield and Newcastle. In making his argument for taking this approach he talked about the agglomeration benefits that accrue to big cities like London from simply being big. He was also implicitly suggesting that individually the big northern cities are not big enough to experience these agglomeration benefits. This same suggestion was also made by Evan Davies in his recent BBC programme ‘Mind the Gap’.
Their suggestions are in part based on the size we would expect our major northern cities to be if they satisfied the empirical regularity known as Zipf’s Law. The excerpt below from one of Professor Henry Overman’s blogs sets out what Zipf’s Law is in relation to cities:
“Many factors contribute to determining the size of different cities in different countries at different times. Despite this diversity, statistical analysis for a wide range of countries suggests that the relative size of cities often satisfies an empirical regularity known as Zipf’s law. A version of this law which is particularly easy to understand is known as the rank-size rule. In a group of cities that obey the rank size rule, the second largest city is half the size of the largest city, the third largest city is a third the size of the largest city etc.”
Henry then produced a graph showing the Zipf plot for English cities which showed that England’s Core Cities are ‘too small’ when their size is compared to London (by the way others have argued that the core cities are the ‘right’ size and London is too big).
This made me curious about how ‘too small’ they are and how much bigger they would need to be in order to comply with Zipf’s Law.
The graph and table below show the differences between the actual size of the UK’s major cities (using PUAs) and the required size to fit with Zipf’s Law. It shows that Birmingham, as the UK’s second largest city, would need to double in size and Manchester would need to add an extra 1.3m people. Even the smallest major city – Nottingham – would need to be more than a third bigger than it currently is. And if you look at travel to work areas (TTWA), because of the size of London’s TTWA, the difference would be even bigger.
Given the focus of the Chancellor’s speech it’s unlikely that creating a ‘super-city’ of the north will become official (or opposition) government policy. Not least because this would raise the knotty issue around which city should be given ‘super-city’ status. Simply looking at population size would lead you to choose Birmingham (I know it’s not in the north), while judging by current economic performance would put Leeds at the top of the list (the strongest big city is actually Bristol but obviously it isn’t in the north either so wouldn’t help deal with the north south issue). If you include good city region governance, then Manchester becomes a strong contender.
Ultimately, whether it’s one super-city or several well-connected cities helping to re-balance the economy, they would need to be given the kind of policy privileges that London currently receives (Mayor & GLA, TfL, tax raising powers, control over national agencies, etc.) and the investment they need to significantly boost the size and productivity of their economies.
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