Where People Live
Unlike the more generic measure of ‘net density’ presented in the previous pages, residential urban density measures how many people live in relative proximity in cities, shown below by the number of people living in each square kilometre of a 100 x 100 kilometres urban region. Residential density is largely driven by topographical constraints, the location of public transport and other infrastructure, but also by each city’s inherited traditions of urban culture and development. Density differs widely, from the high densities of Hong Kong, Mumbai and central areas of Istanbul and Shanghai to the much lower density pattern of London. Johannesburg shows limited areas of higher density set around a downtown that no longer has a residential population, in the midst of a very low-density sprawl. Istanbul, New York and Hong Kong show how topographical constraints drive densities that rise to ‘spikes’ in Manhattan and parts of the Bronx, Brooklyn and Queens in New York, and in Hong Kong Island and Kowloon in Hong Kong. São Paulo is multi-centred and similar in its overall density pattern to Mexico City, yet São Paulo’s skyline is dominated by high-rise apartment blocks, while Mexico City’s is consistently low-rise, demonstrating that high-density can be achieved with different types of built form.
Signs of ageing
The age distribution among urban populations reveals a considerable variation that closely mirrors national and global demographic trends. Hong Kong, along with European and North American cities, reflects a more mature average age compared to cities in developing countries, even though New York and London have younger populations than rural areas in the US and UK respectively. These cities reveal a ‘middle-age spread’ in line with declining birth rates and longer life expectancy. The story is different in contexts of rapid urban growth. The age pyramids of Mumbai and Mexico City – and to some extent Istanbul and São Paulo – show the dominance of younger rural-to-urban migrants, with many residents below the age of 30 providing a broad base for the labour force and the large informal sector they work in. Shanghai graphically represents the ageing structure of its population, reflecting China’s one-child policy and heavy in-migration from rural areas. The remarkable drop in life expectancy, especially among men, of people above the age of 50–60 is noticeable in Mumbai, Istanbul and Johannesburg, indicating limited access to health care, high levels of poverty and poor environmental quality.
Infrastructures of Mobility
Transport infrastructure is a critical driver of urban form, enabling the centralisation of economic functions and the accommodation of a growing population. Without public transport, space-hungry motorways dominate, resulting in more sprawl and congestion. The oldest and most extensive metro, bus and rail systems are in London and New York, creating high levels of accessibility. Hong Kong’s younger metro network extends to approximately 250 kilometres (155 miles) through ten lines with further extensions underway, connecting new towns to the CBD. Like Hong Kong, Mumbai and Istanbul are constrained by topography and have developed efficient and affordable public transport. São Paulo and Mexico City, which are not geographically constrained, have allowed the car to dominate, even though Mexico City’s 177 kilometres (110 miles) of metro carries as many passengers daily as London’s 402 kilometres (250 miles). Shanghai is investing heavily in metro and rail transport, while Johannesburg has insufficient affordable public transport and relies heavily – as do São Paulo and Mexico City – on informal and unregulated collective taxis and mini bus services. Despite the recent addition of the Gautrain, Johannesburg’s rudimentary transport system fails to connect to the places where most people live.
How people travel
How people travel within cities reflects the provision of public transport, local economic development, climate and urban form. Public transport accounts for 40 and 50 per cent respectively of all trips in London and Hong Kong, and 60 per cent of work trips in New York. In Hong Kong, nearly 45 per cent of trips are made on foot which, together with high public transport rates, gives it the greenest modal split of Urban Age cities in the developed world. Despite differing economic profiles, nearly as many people drive in Johannesburg as they do in London, reflecting the dearth of any form of affordable public transport system in the South African city. A third of all trips in São Paulo and Mexico City are made by private car, but just 6 per cent in Mumbai. Non-motorised transport rises in less developed, dense cities: 45 per cent of trips are on foot in Istanbul, and in Mumbai and Shanghai more than half are on foot or bicycle. Shanghai has experienced rapid growth in public transport use, while cycling remains prevalent (despite having dropped dramatically and being banned from some central streets): a feat not achieved by any other UA city. Even where there is a good metro system like in Mexico City, informal transport often dominates, reflecting a mismatch between travel patterns and infrastructure as well as the relatively high cost of public transport.
Urban Age cities compared
Behind the statistics of global city growth lie very different patterns of urbanisation, with diverse spatial, social and economic characteristics that dramatically affect the urban experience. In addition to standard measures of population growth and density, the economy and transport use, LSE Cities has assembled data from a range of official sources on energy consumption, global CO2 emissions and health, allowing a preliminary assessment of how these nine world cities compare to each other on key performance indicators.
A graphic summary of these results offers some striking differences, especially when it comes to their speed of growth. While São Paulo has grown nearly 8,000 per cent since 1900 and London by only 16 per cent (having experienced its major growth spurt in the previous century), it is Mumbai that is predicted to grow the fastest of the nine, with 44 additional residents each hour by 2025. London, however, will only gain one person per hour, Johannesburg three and Hong Kong seven. These trends mask different patterns of age distribution: close to a third of the residents of Mumbai, Johannesburg, São Paulo and Mexico City are under the age of 20, while in Shanghai and Hong Kong the younger generations shrink to 20 per cent or less. Patterns of habitation also differ significantly. The populations of Hong Kong and London are very similar in size, but the population densities within a 10-kilometre (6-mile) radius from their geographical centres (Tsim Sha Tsui, Kowloon in Hong Kong and Trafalgar Square in London) differ by a factor of three. Shanghai’s central area density is as high as Hong Kong’s, but drops off sharply beyond a 10-kilometre (6-mile) radius, while Hong Kong remains dense across the built-up urban region.
Of all the Urban Age cities, Hong Kong possesses the lowest murder rate, of less than one homicide per 100,000 inhabitants a year: safer even than Istanbul and Mumbai with less than three each. São Paulo, Johannesburg and Mexico City prove to be the more dangerous places to live – ranging from 13 to 21 murders per 100,000 people. With the exception of Hong Kong, these findings are paralleled by the level of income inequality indicated by the Gini coefficient – a measure of income distribution with a higher number representing greater inequality – in each of these cities: Johannesburg, São Paulo and Mexico City are the most unequal cities, followed closely by New York, with London being the most equitable. Hong Kong is the exception, being the only city that is both unequal and safe.
GDP per capita is highest in the global cities of London and New York (US$60,831 and US$55,693 respectively), followed by Hong Kong (US$45,090). People living in these three cities are many times wealthier, on average, than in other Urban Age cities such as Istanbul and São Paulo (US$ 12,000–13,000) and Johannesburg, Shanghai and Mumbai (less than US$10,000). Yet despite the fact that Mexico City’s per capita income is less than a third of New Yorkers’ (US$18,321 versus US$55,693), residents of Mexico City own nearly twice as many cars (360 per 1,000 people versus 209) and use roughly the same amount of water per person as Londoners (324 litres/570 pints per day). While Johannesburg, London, Hong Kong and Mexico City contribute similar levels of CO2 emissions per person, the number doubles in Shanghai, where more than 10,000 kilograms (22,046 lb) per person are produced every year, owing to the presence of heavy manufacturing industry in its vast metropolitan region. In contrast we can see Istanbul, with close to 38 per cent of its workforce in the manufacturing sector, the highest of the Urban Age cities, producing just 2,720 kilograms (5,996 lb) of CO2 per person, while Mumbai’s residents contribute only 371 kilogram (818 lb) per person – less than 10 per cent of that of residents in other global cities.
There is significant variation in life expectancy among the Urban Age cities, reflecting a multitude of factors, including the quality of health infrastructure, effectiveness of national public health policies as well as environmental and social conditions. On average, a Hong Konger lives 30 years longer than a resident of Johannesburg and still ten years longer than a person who is brought up in Istanbul or Sao Paulo, while residents of Shanghai can expect to live three years longer than New Yorkers. In Mumbai, although life expectancy has not yet reached 70 years, it performs well compared to the national average of 62 years.