City Evolution: Balancing Concentration and Dispersion

City Evolution Unveiled: How Fewer, Bigger, and Flatter Cities are Shaping Our World

Soraya Malik in Business & Economy December 2025 • 4 min read.

"Discover the hidden forces driving urban change and what it means for you, including the trends in Japan that mirror global shifts."

Cities, the hubs of modern economies, are currently experiencing a transformation across the globe. In many countries, a distinct pattern has emerged: cities are becoming fewer in number, larger in size, and increasingly spread out. This phenomenon challenges conventional understanding and sparks the crucial question of what is causing this evolution.

One key factor appears to be transport access. Advances in transportation have fostered the concentration of economic activities in fewer, bigger cities, while also contributing to the decentralization of these urban centers. The interplay between these forces of concentration and dispersion is critical to understanding the changing urban landscape.

A close look at the evolution of Japanese cities between 1970 and 2020 provides a striking example. With the construction of high-speed railway and highway networks, Japan witnessed a significant decline in transport costs. During this period, the population concentrated in fewer, larger cities, even as each city became more decentralized. The population rank-size plot in 2020 shows a steeper slope than in 1970, the population share of the top 100 cities increased, and cities became flatter and more spread out. This dual evolution, also observed in other countries like China, France, and the US, suggests broader, underlying mechanisms are at play.

Understanding the Forces Behind Urban Evolution

City Evolution: Balancing Concentration and Dispersion

Two primary types of dispersion forces—those operating within a city (local forces) and those extending beyond city limits (global forces)—explain this dual evolution. Understanding these forces is essential for predicting future urban trends and informing policy decisions.

Dispersion forces within a city, such as competition for limited land, primarily affect the city's residents. When transport costs decrease, the relative benefits of concentrating in a congested central location diminish. This leads to a flatter, more spread-out population distribution within each city, balancing the costs and benefits of agglomeration.

Local Dispersion Forces: Effective within each location, such as competition over land.
Global Dispersion Forces: Extend beyond each location, like market crowding.

Dispersion forces that spill over beyond a city, like market crowding, make locations near the city less attractive. As transport costs decrease, competition intensifies over a wider area around each city. This results in fewer cities, each with larger distances between them. The model's comparative static results and policy implications depend heavily on the type of dispersion forces at play. This highlights how transport improvements impact where people live and work.

The Future of City Planning: Balancing Concentration and Dispersion

Understanding the dynamics of urban evolution is crucial for effective city planning. By recognizing the interplay between local and global dispersion forces, policymakers can create strategies to promote sustainable and equitable urban development. Whether it involves managing transport infrastructure, land use, or economic incentives, the key lies in fostering a balance that maximizes the benefits of both concentration and dispersion, shaping cities that are not only economically vibrant but also livable and resilient.

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This article is based on research published under:

DOI-LINK: https://doi.org/10.48550/arXiv.1912.05113,

Title: Spatial Scale Of Agglomeration And Dispersion: Number, Spacing, And The Spatial Extent Of Cities

Subject: econ.gn math.ds nlin.ps q-fin.ec

Authors: Takashi Akamatsu, Tomoya Mori, Minoru Osawa, Yuki Takayama

Published: 10-12-2019

Everything You Need To Know

What key factors are driving the transformation of cities into fewer, larger, and more spread-out entities?

The evolution of cities into fewer, larger, and more spread-out entities is primarily driven by transport access improvements. These advances have facilitated the concentration of economic activities in fewer, bigger cities, while simultaneously contributing to the decentralization of these urban centers. This interplay between concentration and dispersion forces, shaped by decreased transport costs, is a critical factor. Also, dispersion forces, both local and global, play a significant role in this transformation. Local dispersion forces, such as competition for limited land within a city, and global dispersion forces, like market crowding, contribute to the changing urban landscape.

How have transport cost reductions impacted the evolution of cities, and what specific examples illustrate this?

Reductions in transport costs have significantly impacted city evolution. They've fostered the concentration of economic activities in fewer, larger cities, and simultaneously contributed to their decentralization. The construction of high-speed railway and highway networks in Japan between 1970 and 2020 provides a clear example. As transport costs decreased, Japan's population concentrated in fewer, larger cities, even as each city became more spread out. This dual evolution, also seen in China, France, and the US, underscores the broad influence of transport improvements.

What are the key differences between local and global dispersion forces, and how do they influence urban development?

Local dispersion forces operate within a city, affecting its residents. Examples include competition for limited land, leading to a flatter, more spread-out population distribution within each city as transport costs decrease. Global dispersion forces extend beyond city limits, such as market crowding, making locations near the city less attractive. As transport costs decrease, competition intensifies over a wider area, leading to fewer cities, with larger distances between them. Both types of dispersion forces are crucial for understanding urban trends and informing policy decisions.

How does the balance between agglomeration and dispersion forces influence the shape and structure of cities?

The balance between agglomeration and dispersion forces is critical in shaping cities. Agglomeration forces encourage economic activities to concentrate in specific areas, while dispersion forces cause them to spread out. When transport costs decrease, the relative benefits of concentrating in a congested central location diminish, leading to a flatter, more spread-out population distribution within each city. Policymakers can use this understanding to promote sustainable and equitable urban development by managing transport infrastructure, land use, and economic incentives, fostering a balance that maximizes the benefits of both concentration and dispersion.

What are the implications of these urban evolution trends for future city planning and policy decisions?

Understanding the dynamics of urban evolution is crucial for effective city planning. Policymakers need to recognize the interplay between local and global dispersion forces to create strategies for sustainable and equitable urban development. This includes managing transport infrastructure, land use, and economic incentives to promote a balance that maximizes the benefits of both concentration and dispersion. The key is to shape cities that are economically vibrant, livable, and resilient, considering how transport improvements impact where people live and work. This requires anticipating and adapting to trends such as fewer, larger, and more spread-out urban centers.