to derive the critical features of cities by using these three factors, and, thus, he
focused on the relationships between the factors and sociological characteristics of
urbanism or urbanization, referring to this as the “mode of social life in cities.”
According to the United Nations Population Fund (UNFPA) (2009), urban
populations exceeded half of the world’s population in 2009 and reached 55.3% in
2018. How can we count the urban population, and with which definition of cities?
The authoritative reports on world urban populations have been published by the
United Nations Department of Economic and Social Affairs (UNDESA), Population
Division (UNDESA 2018). The urban population in these reports is based on the
definitions given by individual countries and areas themselves, except for some
cases lacking clear definitions or historical changes in time series data. In other
words, many different definitions have been used for providing statistical data on
urban populations.
The boundary of administrative/municipal units and physical concentrations of
buildings in urban and suburban areas are often arbitrary and artificially set. For this
reason, they may not necessarily be the most suitable units of analysis when a study
is conducted on both local and global scales. Thus, we need to provide a tractable
definition of cities that can be applied in the world in order to analyze and compare
cities. We have created a definition based on the fact that urban populations reached
half of the world’s population in 2009 (UNFPA 2009). Satisfying the condition that
the world urban population is nearly equal to half of the total world population leads
to an estimate for the threshold value of population density in urban areas of
approximately 2000 persons per km
2 (Uchiyama and Mori 2017). See Fig. 1.3.
Choosing a population density threshold of 2000 persons per km
2 thus provides a
tractable definition of urban areas (Uchiyama and Mori 2017). This method is useful
Fig. 1.3 Classes of population density and the cumulative population (Source: LandScan Population Grid (ORNL 2016))
1 Megacities as a Global Center of Sustainability Issues: Overview of the Book
5
focused on the relationships between the factors and sociological characteristics of
urbanism or urbanization, referring to this as the “mode of social life in cities.”
According to the United Nations Population Fund (UNFPA) (2009), urban
populations exceeded half of the world’s population in 2009 and reached 55.3% in
2018. How can we count the urban population, and with which definition of cities?
The authoritative reports on world urban populations have been published by the
United Nations Department of Economic and Social Affairs (UNDESA), Population
Division (UNDESA 2018). The urban population in these reports is based on the
definitions given by individual countries and areas themselves, except for some
cases lacking clear definitions or historical changes in time series data. In other
words, many different definitions have been used for providing statistical data on
urban populations.
The boundary of administrative/municipal units and physical concentrations of
buildings in urban and suburban areas are often arbitrary and artificially set. For this
reason, they may not necessarily be the most suitable units of analysis when a study
is conducted on both local and global scales. Thus, we need to provide a tractable
definition of cities that can be applied in the world in order to analyze and compare
cities. We have created a definition based on the fact that urban populations reached
half of the world’s population in 2009 (UNFPA 2009). Satisfying the condition that
the world urban population is nearly equal to half of the total world population leads
to an estimate for the threshold value of population density in urban areas of
approximately 2000 persons per km
2 (Uchiyama and Mori 2017). See Fig. 1.3.
Choosing a population density threshold of 2000 persons per km
2 thus provides a
tractable definition of urban areas (Uchiyama and Mori 2017). This method is useful
Fig. 1.3 Classes of population density and the cumulative population (Source: LandScan Population Grid (ORNL 2016))
1 Megacities as a Global Center of Sustainability Issues: Overview of the Book
5