Urban Populations Are Not Moving in the Same Direction: The Real Signal of a Dividing Global Urban System

Over the past two decades, urbanization has often been told as a single story: populations concentrate in cities, cities keep growing larger, developing-country cities absorb massive numbers of new residents, and cities in developed countries struggle to maintain vitality under aging pressures. This narrative is not wrong, but it is too coarse. This global study by Nature Cities reminds us that what is really happening is not a single, unified urbanization process, but a global urban system that is simultaneously diverging in scale, age structure, gender structure, and migration mechanisms.

Covering more than 10,000 cities worldwide from 2000 to 2020, the study provides rare population evidence at the city level. Several of its conclusions may look like demographic findings on the surface, but in fact they point to deeper strategic shifts in cities: the world’s cities are no longer evolving along the same path, and urban competition is no longer just about “who grows faster,” but about “who can keep operating under what kind of population structure.”

The most notable change is in the global urban dependency ratio. The ratio of children and older adults to the working-age population fell from 0.87 to 0.59. This means that, overall, urban population structures are moving in a more “supportable” direction: the relative share of the working-age population is rising, which in theory is favorable for productivity, the tax base, and economic expansion. For many countries, this should be the so-called window of the “demographic dividend.”

The problem, however, is that this global average masks enormous disparities. Cities are not a uniform entity, and even cities within the same country may be at completely different stages of the urban life cycle. The study shows that small cities are consistently younger than large cities, especially in Africa. This is not a marginal phenomenon, but an important clue to the future urban system: the cities with the strongest population growth, the youngest age structures, and the weakest infrastructure are often not the national primate cities, but those long-neglected secondary cities and small and medium-sized cities.

This directly challenges the inertia of urban governance in many countries. Traditional planning often channels resources into capitals, megacities, or a few growth poles, assuming that they represent the direction of national urbanization. But in Africa, South Asia, and parts of Southeast Asia, the places that truly absorb new population, sustain rural–urban linkages, and take in employment shifts are precisely these smaller but fast-growing cities. They not only determine the quality of urbanization, but also the stability of food systems, regional markets, and local public finances. In other words, future urban competition is not just competition among big cities, but a restructuring of the hierarchical order within urban clusters.More concerning is the divergence in gender structure. The study finds that some cities in the Middle East and North Africa have a clear male surplus, consistent with patterns of labor migration. For urban scholars, this is not new, but its significance lies in the fact that gender imbalance has never been merely a demographic issue; it is a composite signal of labor market structure, residential patterns, social service provision, and political stability. Large inflows of young men, short-term employment, weak family settlement, and high mobility often shape a social ecology different from that of “family-oriented cities.”

From Dubai and Doha to the new development zones around Riyadh, labor-driven migration has accelerated urban construction and also changed the logic of urban governance. These cities are not simply “more international”; rather, they are more dependent on cross-border labor, project-based capital, and intensive investment in infrastructure. Their growth model shows that cities are no longer merely places where populations gather, but instruments where global labor, capital, and institutional arrangements converge. Here, gender structure is not a sociological detail, but a visible indicator of the urban economic model.

Another key finding is that about 45% of urban growth comes from net migration, and 55% from natural increase. This ratio is very important because it means urban expansion is neither driven entirely by birth rates nor entirely by immigration, but by the combined effect of both. For policymakers, this means urban planning can no longer focus only on fertility rates or total population; it must also address the interactions among migration, housing, employment, education, and public services.

In many low- and middle-income countries, net migration is often underestimated because population mobility is far more complex than statistical systems can capture. Rural-to-urban migration, urban-to-urban migration, regional seasonal mobility, conflict- and climate-driven migration, and cross-border labor flows together shape the real picture of urban populations. National averages often “smooth out” these differences, but urban governance cannot rely on a smoothed reality. Housing shortages, overloaded infrastructure, the expansion of informal settlements, public health pressures, and traffic congestion often first erupt in the cities facing the greatest migration pressure.

This is also why the greatest significance of this study lies not in the several attractive global averages it provides, but in proving that national-scale statistics are losing their ability to explain urban reality. When urban population structures have already diverged sharply within the same country, continuing to formulate urban policy using national average age, national average dependency ratios, and national average migration rates is like using a nationwide weather forecast to decide whether a particular valley should prepare for flooding.This mismatch is especially evident in the Global South. African cities as a whole remain young, yet there are wide differences among them: some cities are still rapidly absorbing young workers, while others are already facing the risk of failing to keep up with infrastructure demand. Some cities in Latin America have long entered phases of maturation and aging, yet they still bear the pressure of large-scale informal expansion. South Asia presents an even more complex mixed picture: primate cities are highly concentrated, secondary cities face enormous population pressure, and regional infrastructure has not upgraded in step. The differences among cities are not only a matter of different stages of development, but also the result of different national governance capacities, land institutions, transport networks, and industrial layouts.

This also explains why “small and medium-sized cities” are becoming the new front line of global urban strategy. For a long time, international development policy and investment logic have favored large cities with greater visibility, because they have more complete data, deeper markets, and more concentrated capital. But from the perspective of demographic structure, many countries’ true future growth points, service gaps, and bottlenecks in adaptive capacity are precisely concentrated in small and medium-sized cities. They determine whether regional populations can be effectively accommodated, whether agricultural hinterlands and urban markets can be smoothly connected, and whether climate shocks will be amplified at nodes with weaker governance capacity.

If the core of urban competition in the 20th century was industrialization and economies of scale, then urban competition in the 21st century increasingly resembles a composite competition over demographic structure, migration attraction, spatial resilience, and governance capacity. Whoever can attract and retain working-age populations, provide affordable housing for young families, and maintain public services amid heat waves, floods, and air pollution will be more likely to hold an advantage in the urban system of the coming decades.

From this perspective, the key to the city’s future is not just “growth,” but “sustainable demographic allocation.” If a city only grows in numbers but cannot form a stable age structure, gender balance, and employment absorption capacity, its prosperity may only be temporary. By contrast, some cities that grow more slowly or even experience population stagnation, if they can maintain population quality through industrial renewal, public-service reform, and spatial reorganization, may well possess longer-lasting competitiveness.

This study also suggests a more long-term trend: the global urban system is shifting from “single-center expansion” to “multi-node differentiation.” The importance of primate cities remains, but that does not mean they will automatically become the sole destination for all resources. As regional economic belts, cross-border supply chains, climate migration, and digital work models change, more cities will enter the global network through specialized roles. Some will be manufacturing nodes, some logistics nodes, some energy nodes, and some migration and service nodes. The value of cities is shifting from “how large they are” to “what role they play in the network.”This is also a reminder for national strategy. If a country continues to view cities as administrative jurisdictions rather than spatial assets in competition, it will underestimate the policy pressure brought by demographic changes. Education, healthcare, housing, transportation, water supply, disaster prevention, and the labor market must all be redesigned at the city level. The future competition among nations will, to a large extent, manifest as competition in urban governance capacity; and the core of urban governance capacity is a precise understanding of population flows and demographic structure.

Therefore, what this study truly reveals is not the common-sense notion that “urban populations are changing,” but a far more serious reality: global urbanization has entered an era of heterogeneity. The one-size-fits-all formula for urban development is losing its effectiveness, national averages are losing explanatory power, and the old “big cities first” and “total population orientation” approaches are increasingly unable to address real-world problems. Cities must be understood as dynamic demographic systems, not static administrative units.

In this sense, the most important urban capability of the future may not be the ability to expand, but the ability to identify differences, adapt to differences, and manage differences. Whoever can better and earlier understand the differentiation in urban population structures will have a greater chance of taking the initiative in the next round of global urban competition.