Andrew Nelson with the Global Environment Monitoring (GEM) of the European Community, has developed an interesting map reflecting the access time to cities and areas of more than 50,000 inhabitants in the world.
One of the most relevant data shows that 95% of the world population lives in only 10% of the territory.
The map was done based on the year 2000 data. From the image, a higher resolution PNG file can be accessed.
This document is identified under the following reference:
Nelson, A. (2008) Travel time to major cities: A global map of Accessibility. Office for Official Publications of the European Communities, Luxembourg. DOI:10.2788/95835, ISBN:978-92-79-09771-3.