Urban/rural population ratio: In 2007, the world urban population exceeded the number of people living in rural regions for the first time. As a comparison: In 1800, only 2% of the world’s population were urban dwellers, in 1950 their share had risen to 30%, and in 2000 to 47%. And the number is constantly rising: according to UN forecasts almost three quarters of all people are expected to live in a city by 2050. China and India have the biggest share of people living in cities. It is a well known phenomenon that urbanisation is progressing in the industrialised nations of the West. It is less known that in Latin America and in the Caribbean region more than 75% of the population live in cities today.

Number of large cities: In the past 50 years, the number of cities with more than 1 million inhabitants has increased considerably. Their number has gone up from 80 to 365, increasing fourfold. And there are already 130 cities with over 3 million inhabitants worldwide.

Ranking of megacities: Depending on the definition of the spatial and administrative city borders, the rankings of the world’s megacities vary. UN HABITAT, a programme of the United Nations to promote socially and ecologically sustainable living conditions in cities, lists a total of 22 megacities for the year 2015:

1. Tokyo (35.5 Mio. INHAB.)
2. Mumbai (21.9 Mio. INHAB.)
3. Mexico City (21.6 Mio. INHAB.)
4. São Paulo (20.5 Mio. INHAB.)
5. New York (19.9 Mio. INHAB.)
6. Delhi (18.6 Mio. INHAB.)
7. Shanghai (17.2 Mio. INHAB.)
8. Calcutta (16.9 Mio. INHAB.)
9. Dhaka (16.8 Mio. INHAB.)
10. Jakarta (16.8 Mio. INHAB.)
11. Lagos (16.1 Mio. INHAB.)
12. Karachi (15.1 Mio. INHAB.)
13. Buenos Aires (13.4 Mio. INHAB.)
14. Cairo (13.1 Mio. INHAB.)
15. Los Angeles (13.1 Mio. INHAB.)
16. Manila (12.9 Mio. INHAB.)
17. Beijing (12.9 Mio. INHAB.)
18. Rio de Janeiro (12.7 Mio. INHAB.)
19. Osaka-Kobe (11.3 Mio. INHAB.)
20. Istanbul (11.2 Mio. INHAB.)
21. Moscow (11.0 Mio. INHAB.)
22. Guangzhou (10.4 Mio INHAB.)

As a comparison: Berlin (3.4 Mio. INHAB.)

The first megacities: Still in 1950, New York and Tokyo were the only megacities, in 1975, Mexico City joined as the first metropolis of the South.

Historic megacities: Cities that in relation to the overall population of a county can be considered a big city existed as early as ancient advanced civilisations. Babylonia had approximately 300,000 inhabitants in about 1800 BC and the Chinese Xian had over one million people in about 900 AD. Rom, Bagdad and Beijing had some hundred thousand to one million inhabitants respectively in the Ancient World or in the 11th or 16th centuries.

The fastest growing megacities: Today, the fastest growing city is Lagos in Nigeria: between 2000 and 2010 the population growth amounted to 2.9%. Second place: Dhaka in Bangladesh with 2.6%, the third is Delhi in India with 1.9%.

High population density: The megacity with the highest population density is Mumbai with 27,000 people per square kilometre. In Lagos it’s 20,000. As a comparison: in Berlin 3,851 people live on one square kilometre.

Slum development: Today, 1 billion people live in slums, almost all of them in developing or emerging countries. Worldwide, almost one-third of all city dwellers live in slums (32%), in developing or emerging countries even 43%. According to UN HABITAT the global slum population might rise to 1.3 billion by 2015 and to approximately 2 billion by 2030.