Pancakes to Pyramids: City Form to Promote Sustainable Growth
by The World Bank | Published on 31 May 2021
Towns and cities are economic and social microcosms in which large numbers of people and firms interact. These interactions largely shape how a city looks, how it functions, and how it grows. But how exactly does this many-sided relationship work? What are the specific drivers of urban economic and spatial development? Pancakes to Pyramids brings us closer to answering these questions, beginning with an idealized contrast between two patterns of urban spatial growth. Pancakes are cities that grow outward and remain relatively low-built. Pyramids are cities that grow partly outward, but also partly inward and upward, filling vacant parcels and adding height to central districts to increase economic and residential densities. Both types of density can help cities overcome the challenges that come with population growth, and most urgently, evolving from a pancake into a pyramid, creating a platform with more options for controlling greenhouse gas emissions. This report draws on new evidence, econometric analysis, and predictive modeling to relate the economic growth of cities to their past spatial evolution, and to the possibility and conditions for future pyramidal growth.
- New empirical analysis of the shape and growth of nearly 10,000 cities around the world and rigorous economic modeling finds that the most successful urban areas are those that connect physical growth to economic demand and support this with good plans, policies and investments that help avoid uncontrolled sprawl.
- Using data to understand what makes a city grow outward, inward or upward can help us better understand the interplay between city density and public transport and non-car modes of transportation, to help cities reduce their climate footprints.
Managing city growth requires that city leaders solve a three-dimensional problem.
- City leaders will need to plan and prepare for urban growth along all three dimensions—not only the vertical layering and infill development that will be enabled by future economic productivity, but also horizontal growth that will occur at the city’s edge.
City growth is driven by economic fundamentals.
- The forces that peak a city’s skyline, signaling high demand for floor space in the central business district, are those of economic agglomeration. They are the same forces that drive production of goods and job creation.
Flexible regulations are needed for urban redevelopment.
- Regulations need to be adaptable to changing demand and supply conditions, anticipating the emergence of new uses for scarce urban land.
- Also important here is to conserve irreplaceable cultural and natural amenities—these have not only intangible permanent value, but also a unique potential to create economic value and attract investment through neighborhood regeneration.
- A principal factor in setting a city’s growth path is its plan for networked infrastructure, including roads and transit arteries between the city center and periphery.
- Some capital investments are best to plan for—or even finance and execute—in the earlier spatial development stages, when cities stand to benefit disproportionally over the life of the investment.
Some interesting takeaways from the report include:
The growth of urban built-up area worldwide is not as large as conventional wisdom suggests.
- Between 1990 and 2015, urban built-up area worldwide grew by 30 percent, or 66,000 km2, the size of Sri Lanka, through both horizontal spread and infill. In developing countries, total urban built-up area increased by 34 percent. Significant, but not quite the explosive and rapacious expansion estimated in many recent studies.
Horizontal growth is inevitable for most cities in most developing countries.
- In low-income and lower-middle-income countries, 90 percent of urban built-up area expansion occurs as horizontal growth.
- Nevertheless, there is a silver lining: in high-income and upper-middle-income country cities, a larger share of new built-up area is provided through infill development. For example, a city in a high-income country that increases its built-up area by 100 m2 will add about 35 m2 through infill development and 65 m2 through horizontal spread. But a similar city in a low-income country will add about 90 m2 through horizontal spread and only 10 m2 from infill.
Increasing economic productivity and rising incomes are indispensable for vertical layering, because building tall is capital intensive.
- A city that grows in population, but not in productivity and incomes, will not generate enough economic demand for its spatial expansion to keep pace with population growth.
- Our econometric results show that:
- If a city’s population doubles but incomes stay constant, the city’s floor space per person declines by 40 percent.
- If per capita income doubles but population stays constant, the city’s total floor space per person increases by 29 percent.
- Building tall is capital intensive–so increasing productivity and incomes are critical for a rise in floor space per person through vertical layering and pyramidal growth.
Dysfunctional urban land markets, along with zoning and restrictive building regulations, are factors that can work against taller structures, economic density and pyramidal growth.
- In developing country cities, a lack of legal clarity in land tenure often deters investors from sinking capital into formal structures and contributes to the persistence of slum areas.
Improved transport technology enables economic concentration in urban cores, supports cities’ economic and spatial growth, and boosts demand for livable residential floor space.
- Many developing country cities today struggle with the high road congestion and commuting costs—in time and money—that result from poor transport infrastructure and limited public transit options. Such congestion impedes the separation of residence from the workplace, limiting cities’ spatial expansion along with their economic growth and productivity.
 Forecasts by Jones et al (2021), prepared for the European Commission using the Degree of Urbanization approach, predict that total urban land area will grow 29 percent between 2015 and 2050—in line with the spatial growth rates we measure here for 1990–2015.
Pancakes to Pyramids was funded by the Swiss State Secretariat for Economic Affairs (SECO) through the World Bank Umbrella Multi-Donor Trust Fund Sustainable Urban and Regional Development (SURGE), and the Global Environment Facility (GEF) through the Global Platform for Sustainable Cities (GPSC).
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