During the next decades urbanisation will become one of the most challenging aspects of the world population process, especially in terms of sustainability. The increasing number and size of the world’s large cities in less (LDCs) and least (LLDCs) developed countries has been attracting the focus of the media and policy makers for some time. The fast growing share of people living in large cities, mostly due to a migration surplus originating from surrounding rural areas, is now widely recognised as a threat to long-term development objectives of the affected countries. The expansion of the urban population is resulting in the emergence of new slums with insecure and unhealthy living conditions and an under provision of sufficient jobs, housing and infrastructure.

Between 1950 and 2000 the number of the global urban population multiplied from 0.75 billion to 2.9 billion people, accordingly from 29.8 % to 47 % of the total population. During the last 50 years the average annual growth rate of the world population was 1.75 %, lacking far behind the increase of the urban population with an average rate of 2.68 % per annum. The UN projection of the 2001 World Urbanisation Prospects forecasts a further growth of the urban population up to 4.9 billion, so that the urbanisation ratio will reach about 60 % in 2030. According to this projection most of the expected global population increase will be realised in urban areas and the urbanisation will continue to gain from the migration surplus of rural areas, where fertility will remain considerably higher than on average.

The number of mega cities will rise as well. While in 1950 New York was the only city belonging to the top class of the urban hierarchy, up to now an additional number of 16 cities reached the threshold of 10 million inhabitants. Today a small number of approximately 3.7 % of the world population lives in mega cities, in 2015 this share is estimated to reach 4.7 % (21 cities), causing an unprecedented change of the urban system.

The article is based on the UN estimates and projections of the latest 2001 World Urbanisation Prospects revision. The analysis of the urbanisation process describes the regional patterns of the population distribution in urban and rural areas for the period of 1950 to 2030. In addition aggregated values of key urbanisation indicators are presented as well as figures on the development of different settlement sizes. The results are given grouped by selected regions and for less and least developed countries. A final section discusses the structure and demographic causes of the urbanisation and highlights the consequences for the future urban development policy.

* Original title: Globale Verstädterung – Entwicklung, Ursachen, Folgen (full text in German only)