Ed Glaeser, Giacomo Ponzetto, and Yimei Zou recently published a new academic paper called, Urban Networks: Spreading the Flow of Goods, People and Ideas.
The paper looks at whether it’s more advantageous to build huge and consolidated mega-cities or build connected networks of smaller urban centers (perhaps connected by high speed rail). As countries like China rapidly urbanize, this is something that many people are thinking about.
In China, there is a lively urban planning debate about whether to facilitate the increased expansion of the vast agglomerations of Beijing and Shanghai or whether to focus on creating networks of cities that are smaller, albeit still much larger than almost all of the cities of Western Europe. The current government policy favors networks, in the hope that connected smaller cities may be free of the extreme downsides of mass agglomeration, such as extreme congestion, pollution and high housing costs.
Like most things, there are real trade-offs.
In the paper, they assume that larger cities lead to more urban amenities, which in turn serves as an important magnet for skilled workers. However, for unskilled workers who may not care/benefit from the same urban amenities, it is possible for them to dislike the bigger cities. In this case, the benefits do not outweigh the negatives of urban expansion and an urban divide is created (rich/poor).
One of the potential negatives is housing.
The attraction of denser, not larger, mega-cities is determined also by the elasticity of housing supply. When it is easy to add extra homes on a narrow plot of land, as in Texas, then density becomes more attractive. European urban networks may well be the right answer because history and regulation makes it so hard to build in Europe’s older cities. Even though China has usually been quite friendly towards skyscrapers, the sheer scale of the Chinese population may still make the case for urban networks.
If you’re interested in this topic, there’s a section (#2) in the paper on the history of urban networks that you might like.
One of the reasons I’m so fascinated by cities is that it’s becoming increasingly more important to get them right. From about 1831 to 1925, London was the largest city in the world. Its population went from somewhere around 1.5 to 2 million people to nearly 7.5 million. London surpassed Beijing as the largest city and was then surpassed by New York.
Today our largest cities are significantly bigger. Tokyo has almost 40 million people and London doesn’t even make the top 10. But there’s also a broader shift taking place. According to a new report by the United Nations, most of the world’s largest cities will be in Africa and Asia by 2030. Here’s a chart from Quartz:
And the reason for this shift is because Asia and Africa are newly urbanizing, whereas the rest of the world has already urbanized. In North America, over 80% of people already live in cities.
But even though Asia and Africa are following a trend that has already taken place in the rest of the world, it doesn’t mean we should assume we know what we’re doing. Having spent time in cities like Dhaka, I can attest to the many challenges that these mega-cities are facing and will continue to face as people flood in from the rural areas looking for economic opportunities.
So while it’s important that we talk about strategies for reviving cities like Detroit – which has a population somewhere around 700,000 - 800,000 people – we should also keep in mind that we have some significant challenges ahead of us in terms of creating a sustainable urban planning agenda for the world.