Measuring density

Density is a fundamental measure of urban structure and determines the efficiency of its urban footprint. On these pages, the number of people living in a square kilometre – the ‘ambient population density’ over 24 hours – is represented for the four case study cities. Across an area of 100×100 kilometres, the diagrams illustrate this density of ‘occupation’ in any part of the city over a 24 hour period. They combine a range of socio-economic data – residential location, places of employment, journeys to work – to capture the key spatial dimensions of urban economic life.

The taller spikes in the diagrams represent higher numbers of people concentrated in particular locations – dense residential areas, central business districts, event spaces, shopping streets etc. Flatter zones suggest more residential neighbourhoods of a suburban or low-density nature.

Higher densities can facilitate more sustainable public transport, walking and cycling, making it more efficient to provide services and promote urban vitality. These advantages depend, however, on high-quality urban design and effective city management to minimise the negative impacts of overcrowding, stress and pollution.
While some cities have maintained resident population levels in their central areas, others are losing population from these zones as their boundaries expand. This poses a challenge to cities, as they depend on residents’ taxes to finance urban facilities and infrastructure.

At the same time, most cities have a high percentage of people entering to work each day who do not pay taxes there and often are not represented by the city government as they cannot vote locally. Studying commuters is therefore fundamental to the governance of cities. Tokyo has the equivalent of 20% of its population entering the administrative city every day, while Delhi has 13.5% and Bogotá and London in the order of 9%.

Density differs widely within the four case study cities. Delhi and Bogotá have higher and more concentrated densities in the city core and outskirts while Tokyo and London present lower and more balanced distribution of densities.

Based on LandScan 2010™ High Resolution Global Population Data Set