Chapter 1 Introduction
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Overall, about half of global urban population growth can be ascribed by experts to urbanization (that is, to net rural-to-urban migration) and the other half to natural population growth (McGranahan and Satterthwaite, 2014). Despite the fact that migration’s contribution to urban population growth is moderate, there is much concern about the pace of urbanization and the capacity of national and local governments to cope with its consequences among low-income nations. Policymakers in these countries tend to consider rural–urban migration as the main contributor to over-crowding, congestion, increasing exposure to environmental hazards, and to shortfalls in basic infrastructure and services. Cities are generally conceived as settlement types characterized by certain indicative features such as large populations, density, administrative functions, and social diversity which make them distinct from non-city, suburban or rural areas. The traditional distinction between urban and rural areas in many developed countries has become blurred and the principal difference between urban and rural areas in terms of the circumstances of living tends to be the degree of concentration of population. The differences between urban and rural ways of life and standards of living tend to remain more significant in less developed countries. However, the rapid urbanization in the latter is increasingly linking the cities with their surrounding areas. Key issues regarding definitions are as follows: • No internationally agreed definition of a “city”, nor any consensus on how to identify when a settlement is “urban” or to determine its boundary, as illustrated by the diversity of national urban definitions reported in the World Urbanization Prospects, 2011 Revision (UN DESA, 2012). • Urban areas are defined differently in different countries. Some countries adopt a simple definition based on population size and density criteria, whereas other countries have multiple criteria including size, density and administrative level, and other indicators such as urban employment (for example non-agricultural workers), facilities (such as higher-level schools), and infrastructure (for instance street lighting). Not only are there diverse urban definitions, but countries change such definitions even from one census to the next. • Most urban population thresholds fall between one and five thousand inhabitants. There are however, some extremes with Sweden defining 200 people as meeting the requirements of an “urban” population to Mali requiring 40,000 people to fulfil the same definition (McGranahan and Satterthwaite, 2014). This variation in the size definition can affect perceptions of regional over- or under-urbanization. For example, India, one of the top ten world economies, has one of the lowest urbanization rates at around 30 per cent. It is argued that it is undercounting urban population based on its restrictive urban definition. • Using new monitoring technologies, attempts are being made to develop and apply more internationally comparable demographic definitions of urban and to move beyond simple rural–urban distinctions towards more complex settlement differentiation. The new methodology of the Organisation for Economic Co-operation and Development (OECD) for defining, monitoring