Most people now live in cities and cities are growing rapidly. We are living in the midst of the urbanization age, an age that started in earnest at the beginning of the 19th century, when people first decided en masse to be closer to other people rather than the land. There is no longer any doubt that sooner or later the great majority of us humans will live in cities.
Still, it is possible to overstate how far we have come along this arc and doing so has important implications.
Recent headlines, citing new figures released by the European Commission, informed readers that “everything we’ve heard about global urbanization turns out to be wrong.” The researchers, using advances in satellite imagery and a global population grid, contend that 84 percent of the world’s population now resides in urban areas, rather than the 55 percent estimated by the UN Population Division in 2018.
In a new working paper for the New York University Marron Institute of Urban Management, we present arguments, backed by ample evidence, contending that the European Commission’s number is implausible if the word “urban” is to retain any familiar meaning.
Our argument breaks down into three main points:
First, according to the International Labour Organization, 27 percent of the global labor force was employed in agriculture in 2015. This, coupled with an estimate of the added increment in village non-farm employment (30 percent) and with household size in rural areas being 15 percent larger than in urban areas, suggests that no more than 60 percent of the world’s population lived in cities in that year.
Second, regularities in the distribution of urban population sizes, known as Zipf’s Law, allow us to estimate the population of cities with more than 5,000 people fairly accurately. Following this model, we estimate that 3.6 billion people lived in cities in 2010, approximately 52 percent of the world’s population.
Third, the low “urban density threshold” adopted by the European Commission results in the inclusion of entire cropland regions as well as more lightly populated fringe areas of cities as urban.
The Commission classifies a density of 300 persons per square kilometer as its urban density threshold. This may seem like a plausible number, but upon deeper examination it turns out to imply that the average area of a single residential plot on the periphery of cities rich and poor would be roughly the size of two football fields.
The result is an overestimation of the footprints of cities, exaggerating their size. Such a low threshold also misclassifies many densely populated agricultural regions as urban. In Java, Indonesia, for example, 96 percent of the population living on cropland is classified as urban.
All told, according to the European Commission, cities occupied 2.27 million square kilometers in 2015 and covered 7.6 percent of the landmass of our planet (although even this seems off: dividing 2.27 million square kilometers by the correct global landmass yields a total urban area of 1.5 percent, according to our math*).
If one intends to believe the European Commission’s estimates, then one can safely conclude that cities should stop expanding right now and that all must be done to contain them. If the world is already 84 percent urban, then one may also conclude that the urbanization age – the relentless migration of people from village to city – is basically over.
We, for our part, believe this trend is by no means over, and that we still have a window of opportunity to prepare cities in less-developed countries to absorb the 2.5 billion more urbanites expected by 2050, many of whom still reside in rural areas today. According to the latest UN figures, for every person added to cities in more developed countries, 18 are added to cities in less developed countries.
In addition to retrofitting and possibly densifying existing cities – which, if we are to believe the European Commission, is all that’s left to do – we believe that preparing cities for their inevitable and massive expansion in the decades to come, all while making cities more productive, more inclusive, more sustainable and more climate-resilient, is the very real challenge now facing us all.
*The European Commission has noted their initial landmass calculation was an error that will be corrected in the 2018 edition of the Atlas of the Human Planet.
Correction, 8/21/18: An earlier map of St. Petersburg contained errors and was replaced by a map of Dhaka.
Shlomo (Solly) Angel is a Professor of City Planning at the New York University Marron Institute and leads the NYU Urban Expansion Program and NYU Stern Urbanization Project.
Patrick Lamson-Hall is a Research Scholar; Bibiana Guerra is an Economist and Urban Management and Development Professional; Yang Liu is a Research Scholar; Nicolás Galarza is Research Scholar; and Alejandro M. Blei is a Research Scholar at the NYU Urban Expansion Program.