Urban Population Dynamics
Improving social and economic conditions for all people and promoting sustainable development is increasingly an urban challenge. As cities grow, making these improvements becomes more complex.
The urban population is growing at a much faster rate than the population as a whole, and by larger annual increments than ever before. By the early years of the next century, most of the people in the world will live in urban areas. In most developing regions the proportion of people living in the largest cities is also increasing.
Cities are intimately tied to national prospects for sustained economic growth and sustainable development. The ability of cities to function as social, cultural and economic centres is shaped by urban population dynamics. This section will review the current urban demographic situation including: problems in defining urban areas; urban population growth since 1950, and its concentration in developing regions (noting regional differences); sources of urban growth, including natural increase and migration fuelled by rural population growth; the world's largest cities (now concentrated in developing countries, especially in Asia); projections of the future size and location of large cities, and the difficulties of projecting accurately; and the continuing growth of rural populations in developing countries, despite outmigration.
"Like people, cities have personalities. Each represents a unique mix of history and natural setting, cultural patterns, and lifestyles. Some are ugly yet attractive, others beautiful but dull. Under such circumstances modelling and theorizing about cities is risky, if even possible."3
Urban systems take a variety of forms in different countries, and diverse definitions of "urban" are used for census purposes. This variability makes comparisons and generalizations difficult. Internationally accepted definitions generally involve some combination of the following:
The particular definitions of cities used by different countries vary considerably and unsystematically. Among those countries that base their definitions largely or exclusively on population counts, some define a locality as urban if it has as few as 200 residents (Iceland and Norway, for example); more common cut-off points are 2,000 (Angola, Argentina, Bolivia, Cuba, Eritrea, Ethiopia, France, Gabon, Germany, Guadaloupe, Honduras, Israel, Kenya, Liberia, the Netherlands, Sierra Leone) and 5,000 (Austria, Comoros, Czech Republic, Ghana, Lebanon, Madagascar, Mali, Saudi Arabia), while some countries put the cut-off point as high as 10,000 (Benin, Greece, Italy, Jordan, Kuwait, Portugal, Senegal).
Since national authorities use their own definitions in reporting on cities, it is not possible to apply a uniform definition or set of criteria to all countries. Given their different social conditions, such an exercise would not necessarily be useful. But the incomparability of the data available underscores the need for carefully designed databases for monitoring urban development and dynamics.
Urban dwellers will soon be a majority of the world's population. Not long after, they will be a majority in all regions of the world.
As the figure below indicates, the percentage of people living in urban areas has increased dramatically during the past half century, particularly in the less-developed regions. The United Nations projects that a majority of the world population will be urban by 2005; in the less-developed regions, that threshold will be crossed before 2015. Of the world's 2.6 billion people currently living in urban areas, over 1.6 billion are in less-developed regions. These regions will include 3.2 billion out of 4.1 billion urban people worldwide in 2015, and over 4 billion out of 5.1 billion in 2025.
The urban population is increasing much faster in developing countries than in the more-developed regions.
In 1970, there were about as many city dwellers in developing countries as in the more-developed regions. The ratio is nearly two to one today; it will pass three to one by 2015 and approach four to one by 2025. Of the 1.23 billion urban residents added to the world population since 1970, 84 per cent have been in less-developed regions, and this proportion is growing. It is projected that less-developed regions will account for 92.9 per cent of a more than 2 billion increase in the global urban population between 1995 and 2020.5
In terms of total population numbers, Asia now accounts for 1.2 billion of the 2.5 billion global urban residents (i.e. about 46 per cent). Europe accounts for 535 million more. By 2025, 23 new urban Asians will be added for every new European urban resident. Latin America and the Caribbean account for about 358 million current urban residents. In 2025, these numbers will be: Asia, 2.7 billion; Europe, 598 million; Latin America and the Caribbean, 601 million; and Africa, 804 million.
There is substantial variation in the level of urbanization within regions. In Africa this ranges from 48 per cent in Southern Africa, 45 per cent in Northern Africa, 36 per cent in Western Africa and 33 per cent in Middle Africa to 21 per cent in Eastern Africa. These differences between African subregions result from historical patterns related to their governance and economic structures dating back to colonial times, and are expected to continue for at least the next 30 years. National levels range from 6.1 per cent in Rwanda6 to 85 per cent in the Libyan Arab Jamahiriya.
For Asian subregions the levels are: South Central Asia, 28.8 per cent; Eastern Asia, 36.9 per cent (the regional statistic is dominated by China's 30.3 per cent); and South-eastern Asia, 33.7 per cent. National levels vary from under 10 per cent in Bhutan to over 90 per cent in Hong Kong and Singapore. In Western Asia, national levels vary from 13 per cent in Oman to over 90 per cent in Bahrain, Israel, Kuwait and Qatar.
Subregional urbanization levels in Latin America and the Caribbean are 62.4 per cent in the Caribbean, 68 per cent in Central America and 78 per cent in South America. National levels range from 13.8 per cent in Montserrat, 31.6 per cent in Haiti and 41.5 per cent in Guatemala to 90.3 per cent in Uruguay and 100 per cent in the Cayman Islands and Bermuda.
Urban growth in less-developed regions is declining, but annual increments will continue to be very large into the next century.
The global urban population is growing by 2.5 per cent per year (3.5 per cent per year in the less-developed regions and 0.8 per cent in the more-developed regions), or 61 million people roughly the equivalent of adding six cities the size of Lagos. Annual urban growth in the less-developed regions peaked at 5.1 per cent during 19551960. Today's rate of growth is slower because the base population is much larger, but the annual increments are greater. By the period 20202025 the global urban growth rate will have declined to under 2 per cent per year, but the urban population will increase by 93 million people more than the current annual increase in the total world population.
As the figure on this page shows, the highest rate of urban growth is in Africa. Cities in Eastern Africa grew by more than 6 per cent a year between 1960 and 1980, reaching a high of 6.5 per cent during 19751980. A gradual decline to 4.1 per cent in 20202025 is anticipated. Southern Africa's urban growth rate, now 3.2 per cent, will decline to 2.3 per cent by 20202025.
Asia accounts for more than two thirds of the annual increase in the global urban population. Within Asia, urban growth rates are more than 3.6 per cent per year in Southeastern Asia and Western Asia, compared to about 3 per cent in Eastern Asia (less if China is excluded). These subregions are expected to reach 2.2, 2.0 and 1.6 per cent urban growth, respectively, by 20202025.
Three different processes fuel urban population growth7: natural growth (the excess of births over deaths), migration from rural areas, and cities' incorporation of rural surrounds (redefinition of administrative boundaries). The relative importance of each component changes as urbanization proceeds.
When urbanization levels are low (particularly when rural and urban fertility rates are similar), migration accounts for most of the growth difference between cities and rural areas. Natural increase becomes more important at higher levels of urbanization.8 When economic opportunities in the cities expand rapidly, growth from migration may also increase.
By way of contrast, the rapid urban growth in Europe during the 19th century was largely attributable to migration, fuelled by the growing urban manufacturing sector. London's population more than doubled between 1801 and 1851. The 10 largest cities in England during this period increased from 16 to 23 per cent of the total national population. This was also a period of substantial migration to North America. It is estimated that if the population which left the United Kingdom had instead moved to its cities, urban growth would have exceeded 5 per cent a year. At this rate, the urban population would have doubled in 14 years, about the pace of urban growth observed in Africa since 1950.
The largest cities
City sizes and growth rates describe only part of the global transformation of where, and how, people live. The distribution of sizes of urban areas is changing dramatically. In 1950, only one city had a population of more than 10 million people. In 1994, there were 14 such cities, only four of which were in more-developed regions. By 2015 there will be 13 more, all in the less-developed regions.
The composition and distribution of the world's largest cities has changed dramatically over the past 45 years.
In 1950, only New York had a population exceeding 10 million. Eleven of the 15 largest cities were in more-developed regions. The 15th largest city, Berlin, had 3.3 million people. In 1970, three cities (Tokyo, New York and Shanghai) exceeded 10 million; seven of the top 15 were in less-developed regions, and the 15th largest had 6.7 million people.
By 1994, 14 of the top 15 cities had more than 10 million people. The largest, Tokyo, had reached 26.5 million (the only city with more than 20 million); 11 were in less-developed regions and the 15th largest city had 9.8 million. By 2015, seven cities will exceed 20 million (Tokyo will still be the largest, at 28.7 million); 13 of the top 15 will be in less-developed regions, and the 15th largest will have nearly 15 million.
Between now and 2010, Asia's share of the 15 largest urban agglomerations18 will grow from nine to 11, Africa's from zero to one. Latin America will go from having four of the 15 largest cities to two, and Northern America from two to one.
The growth rates of megacities have been changing over the past few decades and will continue to do so. The fastest growing megacities will be in the less-developed regions.
Megacities in the more-developed regions grew, on average, by less than 1 per cent per year between 1970 and 1990. Some, such as Los Angeles, Tokyo and Moscow, grew faster, while others, like New York, experienced negative growth.
In contrast, Bombay, Karachi, Lagos and Dhaka grew by 3.7, 4.7, 6.7 and 7.6 per cent, respectively, between 1970 and 1990. These growth rates will moderate before 2015. However, many of the cities projected to be megacities in 2015 will grow by more than 3 per cent per year between 1990 and 2000 (including Bangalore, Bombay, Dhaka, Delhi, Hyderabad, Istanbul, Jakarta, Karachi, Kinshasa, Lagos, Lahore and Metro Manila).
Six megacities are projected to grow faster than 3 per cent per year during 20002015: Dhaka, Hyderabad, Karachi, Lagos, Lahore and Kinshasa. Dhaka's 2015 population is projected to be more than 13 times larger than its 1970 population; Lagos's will be over 11 times larger. Slower growth rates are expected in Istanbul, Lima, Mexico City, São Paulo and Seoul.
The proportion of the population living in the largest cities is increasing.
In 1990, 7.5 per cent of the urban population in more-developed regions was concentrated in the four cities with more than 10 million people; by 2015, these four cities will account for about the same share of the urban total, 7.2 per cent. In the less-developed regions, however, the change will be dramatic: from 98 million people (6.9 per cent of the total urban population) in eight cities of over 10 million in 1990 to 378 million (12.0 per cent) in 23 such cities by 2015.
At the same time, substantial change is expected in the distribution of cities of smaller sizes, particularly in the less-developed regions. The number of cities of 510 million people will increase from 15 to 36 between 1990 and 2015, and the population in them will more than double (from 110 million to 226 million), even as the proportion of the urban population in this size class declines slightly. Cities in the range of 15 million people will increase from 151 to 352, with their combined populations increasing from 283 to 701 million. Both the number and population of those in the 500,000 to 1 million range will increase by about 50 per cent.
Cities of fewer than 500,000 people will continue to account for more than half of the urban population at least through 2015. Those in the less-developed regions will contain more than twice as many people in 2015 than in 1990 (1.64 billion compared to 812 million), though their share of the urban total will decrease slightly. In the more-developed regions, the greatest growth in numbers and population will occur in cities of 15 million people.
Regional patterns of city size distribution and growth vary substantially. In Africa, the proportion of people living in urban areas grew from 14.7 per cent in 1950 to 34 per cent in 1994. In 1950, 80 per cent of the urban population lived in cities of fewer than 500,000 people; this proportion declined to 60 per cent by 1994 and is expected to fall to 54 per cent by 2015. Africans are becoming increasingly concentrated in larger urban areas. Nearly 19 per cent will live in cities with over 5 million inhabitants by 2015, compared to 8.1 per cent in 1994.
In Asia, the number of cities in each of the size classes over 1 million people will more than double between 1990 and 2015. The greatest proportional growth will occur in cities of over 10 million.
Latin America and the Caribbean is the only less-developed region where cities of 500,000 to 1 million will contain a majority of the urban population by 2015. Cities of 15 million will show the largest growth, increasing from 32 to 69 in number, from 61 to 132 million in population, and from 19.4 to 25.2 per cent in their share of the total urban population.
Europe over the next quarter century will see little change in either the numbers of cities or the total populations in the various size groups; nearly two thirds of the population will continue to reside in cities of under 500,000.
In Northern America, the proportional distribution of population among city sizes will change little between 1990 and 2015. Unlike Europe, less than 40 per cent of the urban population is in smaller cities. Oceania's urban population pattern, dominated by Australia and New Zealand, is not expected to change.