Come together?

There's a piece by urban maven Richard Florida on The Atlantic Cities blog, summarising some research on the link between urban density and productivity.  What is perhaps more interesting than the fact that there is a link (talented people and businesses benefit from 'agglomeration' and are drawn to the locations that support it) is the fact that this only works for cities with high levels of skills:

"[the report] notes that density plays a bigger role in cities where levels of skill and human capital are higher. Metro areas with below average levels of human capital realize no productivity gains from density, the study finds, while doubling density in metros with above average human capital gain productivity benefits that are roughly twice the average. This "negative net agglomeration effect" found in less skilled metros leads the authors to conclude that the negative effects of congestion swamp the positive effects of urbanization in less skilled places."

That is to say, densification works for you if you live - put bluntly - in a middle-class professional city, but less well if you are in a low-skilled working class city.  This seems to highlight something that is little remarked on by professional density fans like me, even if it is about people and communities within cities, rather than cities as economic entities.  For all the benefits (viability of local services, lower car dependency, lower carbon impact) that high density urban living can offer, high density means different things for different classes: living in the Barbican and living in the Heygate Estate are different experiences, even if cast from the same concrete.  Notting Hill is not Canning Town.

So how does density relate to deprivation?  In London, the most densely populated wards include both some of the richest and some of the poorest (Tachbrook and Green Street East (in Westminster and Newham respectively)), but the poorer wards are denser overall.  The graph below shows London's 620 wards grouped in order of their average rank in the 2007 Index of Deprivation, with their population density on the vertical axis. 

The co-efficient of correlation is -0.48, which implies some relationship between high deprivation rankings and high density, if not a precise one (IMPORTANT HEALTH WARNING: this blog post involves me using statistical formulae and large datasets, so should be treated with something between suspicion and disdain).  So far, so unsurprising.  Poorer areas are more likely to be in the inner city (so likely to be denser), and also likely to include fewer fripperies like parks that would detract from density (when measured as people per square kilometre, rather than as dwellings per hectare).  Prosperous areas that look dense because they are built up may actually be low density in terms of residents (from, for example, single people or couple living in larger flats with spare rooms).

So, if that's our starting point, how has London been changing in recent years?  The chart below shows actual and projected changes in population density (2001-16), against deprivation rank.

 

Three things are immediately noticeable. The first is that London is becoming denser almost everywhere. Secondly, the curve is a lot more ragged: most wards are seeing a relatively steady change in population, but there are places (like Stratford New Town, Canning Town and Fairlfield) where density is more than doubling.  Finally, it is the poorer places that are densifying most intensively (with a correlation co-efficient of -0.40 between deprivation rank and absolute increase in density). These are the places that are densest, and getting denser: Northumberland Park, Bromley-by-Bow and Mile End are all among the places that are densifying by more than 20 per cent in fifteeen years.

So, what if anything does this all mean?  It means that we need to look at the numbers more closely.  How are inner and outer city areas differentiated, and how does densification relate to changes in prosperity and deprivation?   Is greater density a symptom of improving fortunes, or a cause of them?  Or does densification have the opposite impact on richer and poorer places, boosting prosperity in the former and amplifying the problems of poverty in the latter?  In the meantime, you can note that the densest, and poorest, areas in London are densifying fastest.  It's not clear that this is necessarily a good thing.

(Thanks to London's http://data.london.gov.uk/ site for the figures, and to Paula Hirst for the tip off)

DRAFT POST - TO BE REVIEWED