A secondary city is an urban hub that fills specific regional and local needs related to governance, economics, finance, education, trade, transportation. A secondary city is defined by population, area, function, and economic status, but also by their relationship to neighboring and distant cities and their socio-economic status. A secondary city may emerge from a cluster of smaller cities in a metropolitan region or may be the capital city of a province, state, or second-tier administrative unit within a country. Secondary cities are the fastest growing urban areas in lower and middle income countries, experiencing unplanned growth and development. By 2030, there will be twice as many medium size cities as there were in 1990, outnumbering the total number of megacities. According to the World Bank, secondary cities make up almost 40% of the world cities population. Many secondary cities in the Global South are expected to undergo massive expansions in the next few decades comparable to city growth in Europe and North America over the past two centuries. These cities are unique environments that generally have limited data and information on infrastructure, land tenure, and planning.
Secondary city vs megacities
Secondary cities are often eclipsed by megacities that dominate urbanization programs due to their size and influence. However, secondary cities represent a larger percentage of the urban population worldwide and there are many more secondary cities than megacities. For example, in sub-Saharan Africa secondary cities are experiencing more than fifty percent of the continent's urban growth. The U.N. World Urbanization Prospects 2018 note that approximately only seven percent of the world's population live in megacities of 10 million or more.
Secondary cities have their own socio-economic and political culture that differ from megacities. They have more land, are less developed, and offer more opportunities for investment, adaptation, and improvisation. These cities are important emerging centers of economic activity that relieve the pressures of migration to megacities. While the large cities play a significant role in shaping the economic geography of cities in fostering global trade, travel and investment, it is secondary cities which will have a much stronger influence in the future upon the economic development of countries.
The rapid growth of secondary cities and general lack of infrastructure, particularly in lower and middle income countries, make these cities prime locations for urban sprawl and informal settlements with inadequate basic services. According to UN-HABITAT, "slum population now expands annually by 25 million." Countries like India are developing secondary cities to absorb informal dwellers—as India's chief economic planner, Montek singh Ahluwalia in 2007, observes: "One hundred million people are moving to cities in the next 10 years, and it’s important that these 100 million are absorbed into second-tier cities instead of showing up in Delhi or Mumbai."
Characteristics of a secondary city
Secondary cities are difficult to define and vary from country to country and amongst the variety of urban reporting tools such as the U.N. World Urbanization Prospects and the Atlas of Urban Expansion. Secondary cities reflect their countries' demographic and geographic characteristics. The population of a secondary city may range from 10-50% of the country’s largest city, although some may be smaller than this. Population is a measure of the urban scale but does not reflect the role and function of the city. For example, while a secondary city in Costa Rica will have significant population differences from a secondary city in China, their functional roles may be similar.
Secondary cities can be characterized into three general categories: sub-national functional centers (i.e., provincial capital, industry center, university hub, tourist attraction); city clusters or satellite urban areas surrounding a larger metropolitan region; and an economic trade corridor developing along major transportation routes. These categories define the regional importance of secondary cities and their linkages to the surrounding hinterland and rural areas. Secondary cities have a diffuse genealogy creating a hybrid, socio-cultural urban dynamic often in contrast to larger urban areas. The secondary city is a location for improvisation and innovation. Local patterns of commerce, the interactions of civil society, and decentralized political activities in secondary cities reflect a shifting economies, changing stakeholder alliances, and adaptive governance structures.