Densification: We need to talk about equity

The distribution of resources, wealth and opportunities around the globe is characterised by a lack of fairness — equity — which is a destabilising force testing the resilience of cities around the world.

Densification is one of many ingredients in an urban problem-solving strategy. When used properly, changing population density can also be a powerful tool to achieve greater equity – fairer treatment of all inhabitants — however, how a change in density impacts equity is easily and often overlooked.

In this post I explore how density and equity are interrelated, for 4 types of equity:

1. Spatial equity
2. Economic equity
3. Environmental equity
4. Social equity.

1. Density and spatial equity

Put simply, space is a resource which is not equitably shared in the world. This is evident from the population density variation observed in some of the world’s cities:

This chart shows a person in Mumbai or Dhaka to have amongst the world’s smallest physical footprint (around 25 square metres) whilst someone in Phoenix, San Antonio, Houston or Atlanta has the largest (around 750 square metres). If all the world’s cities were reconfigured to the same density whilst retaining the overall area taken up by cities and infrastructure – 1.5 million square km – they would need to have the density of Beijing, at 5,100 persons per square km.

The chart summarises what we know and generally accept: that there is clearly a lack of spatial (or geographic) equity across cities and countries. The capital of Bangladesh is 45 times more densely populated than the capital of Australia. A detailed discussion of the complex processes that have led to these differences in density is beyond the scope of this post.

2. Density and economic equity

The Gini coefficient is a measure of economic equity, and the below chart relates it to population density. A higher GINI coefficient represents greater wealth disparity and economic inequity.

There appears to be no distinct relationship other than the frontier formed by outliers Johannesburg, Lagos, Hong Kong and Dhaka, beyond which a GINI-density combination does not appear possible.

(The lack of clear relationships in the chart reminds us of the peril of seeking answers to the problems in cities in only a small set of variables.)

However, adding average wealth measured by GDP per capita to the chart and separating geopolitical outliers draws out some noteworthy trends:

Neither richer (blue) nor poorer (grey) cities are bracketed into a narrow range of wealth disparity.

People in the world’s poorer cities (shown in grey) are more tightly packed, with the almost all exhibiting density above the global average.

Separating out China, shown in red (see next paragraph), a clearer inverse relationship between density and wealth disparity seems to emerge for both the world’s poorer cities (in grey), and the world’s richer cities (in blue). For both groups, economic equity appears to improve with density. For rich cities, the trend line is located lower down on the chart: richer cities have better economic equity.

Chinese cities, shown in red, do appear to have some common characteristics (Hong Kong excepted): although their inhabitants are all poorer than the global average they enjoy the greatest level of economic equity (low GINI); they have similar densities (at just above the average global density) perhaps reflecting a standardised approach to spatial planning in these rapidly growing metropolises; and their wealth disparity appears to grow as their connections with the richer West grow (Shanghai and Beijing – and Hong Kong).

Barcelona has a great deal of both density and economic equity. Here density-related factors are likely to have contributed to economic equity: excellent transport, proximity and intense clustering provides easy access by many to a vigorous and dynamic network of cross-fertilisation, innovation and collaboration between industry, education and research institutions across a diverse range of economic activities and specialisms enabled and supported by a large, dense and skilled labour force that can be more productive because of the opportunities on offer. Density boosts the opportunities for a broad cross section of Barcelona’s citizens to participate in and benefit from the economy.

The low levels of economic equity in dispersed cities like Johannesburg and Atlanta — which is represented in the chart above by a high GINI Coefficient — is likely to stem from congestion, poor public transport and long commutes which disproportionally affects those less well-off, making it harder for them to participate in the already much reduced potential collaborative opportunity ‘bumps’ because of the narrower range of enterprises spread too thinly across the city. The economy in a low density city is less accessible to the less prosperous.

Excessive density can harm economic equity. Where very high densities are not accompanied by appropriate levels of public transport, congestion gets in the way of efficient economic interactions. Likewise, overly negative impacts on the quality of life of very high densities may reduce the city’s attractiveness to skilled workers and inward investment.

3. Density and environmental equity

With no end in sight to global population growth and consumption, land continues to get scarcer and climate change and depletion of the natural world demands populations to be increasingly concentrated to reduce carbon emissions and preserve more land for natural ecosystems, agriculture and recreation.

Density’s relationship with environmental equity, represented by per capita greenhouse gas emissions, is explored in the below chart. Again, higher levels of equity, this time of the environmental kind, are associated with higher densities.

(I suspect even clearer trends would be visible if the data is to be adjusted for the effect of a city’s climate – driving heating and cooling – and access to renewable energy sources.)

For richer cities, the trend line is located higher up on the chart, reflecting that energy consumption — and environmental inequity — is generally still proportional to levels of economic activity and wealth. Richer cities consume more energy.

Of the world’s richer cities, Paris, Barcelona and Tokyo are the densest, and have among the lowest per capita greenhouse gas emissions. The density-related phenomena contributing to this raised environmental equity indicator likely include public transport being more viable — and indeed prolific — leading to a reduced reliance on cars, shorter average journeys encouraging walking and cycling, and apartment living reducing the demand on space heating. The right level of density provides a good balance of availability and ease of access to green space.

Low environmental equity in sprawling cities like Denver and Sydney likely results from the higher burden of transport needed to shift people around the city. Demand thresholds for an efficient public transport system aren’t met which, barring sufficient government intervention, leads to a greater reliance on cars.

Dhaka and Mumbai represent cities that are too dense without the right infrastructure — e.g. utilities, public health — to make those densities work to their advantage. Like in low density cities public transport is a problem. Here though, the poorly funded public transport which leads to an over-reliance on road transport and the accompanying debilitating congestion leads to life-threatening pollution. To make matters worse, the lack of proper planning, a contributor to the excessive densities, has led to oversights such as the need for green lungs — parks — being overlooked and/or deemed an unnecessary luxury.

Pollution and poor access to nature both represent social inequity.

4. Density and social equity

Life expectancy at birth is a good indicator of the health component of social equity. The below chart relates it to population density.

For all richer cities (blue bubbles) except Johannesburg, life expectancy at birth appears to bear little relationship to population density, but instead is fairly constant, at around 90%-100% of that of Madrid (85 years). For poorer cities (grey bubbles), there appears to be an inverse relationship between wealth and life expectancy: maximum life expectancy (around 90% of Madrid’s) is found at around the global average population density of 5,100 persons per square kilometre; an increase in density from this appears to bring social disadvantages in the form of reduced life expectancy.

This inverse relationship is particularly evident in the case of Mumbai, which has one of the lowest life expectancies in the world. For Mumbai, a strategy to reduce density may bring about improvements in life expectancy, and thus greater social equity. In doing so, its challenge will be to maintain its relatively high levels of economic equity which would be expected to decrease with lower population density.

Further components of social equity include quality of life of the elderly, and integration of marginal groups such as ethnic minorities. This is explored in more detail in a paper on compact city development by Hege Hofstad.

Neighbourhoods in dense cities such as Hong Kong, Paris, Tokyo and New York contain a good mix of housing forms that allow people to live in the same neighbourhood throughout their life stages, changing accommodation as their needs change. Apartments — the primary typology of denser living — permit elderly people to continue living independently for longer. Apartment block micro-communities offer more chance encounters and social interactions, a protection against the debilitating loneliness so often accompanying old age. Densely clustered services in urban nodes are more easily accessible by the elderly, boosting their ability to continue living independently. As density shrinks distances, it encourages walking and cycling, leading to health improvements. Compact city development not only creates identity, but also engenders a social climate that rejects segregation and enhances diversity and integration. (For more on this topic, see my posts on Circular Economy/Circular Society and Circular Society/Dementia Care.)

Lower densities lead to the opposite effects including poor health due to heavy use of cars and less community infrastructure to allow the elderly to continue living independently. Densities which are too high may also become a hindrance to the independence of the elderly.

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In this post, I have shone a light on the strength of some of the relationships between density and equity which city leaders can rely on to make better decisions. It appears that, in general, higher densities lead to greater equity, or fairness. Vigilance is needed to avoid density’s pitfalls, which above was especially visible in the trend between density and life expectancy for the world’s poorer cities.