One concept I developed for my PhD was the “Tokyo moment”, basically a very large city growing rapidly. I did this to show how much of a trailblazer Tokyo, the world’s first Asian megacity was, and what this might mean for other cities in developing countries. I also used this “moment” to argue why I chose my period of observation as that covering the postwar period until roughly 1970.

I define the “Tokyo moment” as a twenty-year period in which a relatively large metropolitan area (>4.0 million inhabitants at the outset) at least doubles its population. This brings them close to or in some cases above the ten-million-inhabitants threshold, broadly agreed upon as the marker of a megacity.

Using UN Population Division figures, there are (only?) 20 cities having had a Tokyo moment (or having one right now). Note that one city can have multiple “Tokyo moments”. In fact, most developing megacities go through at least two of these moments, showing that their rapid “megacity growth” extends over a period of more than 20 years.

Asian cities claim 13 spots in this list, broadly in line with Asia’s share in the global population. There is only one Western city (LA) and two Latin American cities (Mexico City, Sao Paulo) on the list. Johannesburg is the first of four African cities to experience a “Tokyo moment”, with Lagos and Kinshasa just about done with their first lap.

Doubling a city’s population in 20 years translates into an average annual rate of growth of about 3.5%, which can realistically only work with large-scale migration. This is a feature uniting all of the cities above, just how they managed to deal with such migration varies starkly.

LA, Tokyo and Osaka more or less managed to accommodate migrants without a growth in informality. China circumvents part of this with its hukou household registration system. All other cities saw and are seeing a concurrent growth in slums.

As Asia’s first megacity and the world’s largest urban agglomeration until today, just how instructive is Tokyo’s experience from 1950-1970? A few starters adapted from my dissertation:

• First, Tokyo blurred the boundaries between developed and developing city. The main motor of the 23 wards’ economy in this period was the manufacturing sector, employing almost 40% of the labor force at its peak. It comprised a majority of labor-intensive small-scale producers engaged in what was initially relatively low value-added work. In this, early postwar Tokyo aligns with our understanding of today’s developing cities, whose comparative advantage is explained by the abundant availability of cheap labor. In Tokyo, industrialization and urbanization went hand in hand.
• Second, Tokyo was marked by comparatively low living standards. Despite the difficulty of comparing living standards across time and space, some authors have described the Tokyo of the postwar period as having the phenotype of a “slum” (Echanove & Srivastava, 2013). This relative poverty was a shared experience among the inhabitants of the ward area. Contrary to the megacity discourse and urban development theory, rapid urbanization did not lead to spatial stratification here. In other words, living standards did not differ too widely between different parts of the city. Therefore, Tokyo’s experience fits relatively uneasily with that of other megacities today.
• Third, Tokyo offers a unique case study of the institutions governing megacity growth in historical context. Today, megacities are usually hard to govern due to governmental fragmentation (a multitude of administrative layers), a lack of resources (capital investment requirements are biggest here), weak institutions (the informal sector and business wield outsize control) as well as the interference of national governments in their matters.
• Fourth and finally, the study of Tokyo provides an attempt to historicize the discourse on megacities, which is still in its infancy. While there are important similarities between today’s megacities in terms of their size, organizational complexity and socio-economic challenges, there are important contextual differences that are best assessed using a historical approach. In some countries, megacities are primate cities, while in others, several megacities have developed in tandem. Many megacities exist in increasing isolation from their hinterland, while others are entangled in a close relationship with other cities or regions in their country. Traditionally, urbanization has coincided with industrialization, and the European or American experience has been the yardstick with which to analyze other parts of the world, especially as this model has been exported around the world. However, while many of today’s megacities are also colonial cities, there are varied paths to industrialization, affecting the way that this process has defined cityscapes very differently in different parts of the world.

The cities having a “Tokyo moment” form a relatively exclusive club. They, and a cohort of slightly smaller but rapidly-growing cities stand to gain from the experience of Asia’s first megacity.