Urbanization is the process of human migration from rural areas to cities. Thus, rapid urbanization means that the pace at which migration from rural areas to cities takes place is faster than a country has time to plan for their existence in cities. The situation differs from country to country because the number of cities and rural areas in the countries is different. Another possible reason for this difference is the nature of countries' development; some countries are developed, others are developing while still others are considered least developed. Urbanization in developed areas dates back to the era of industrialization, when people migrated from rural/ancestral areas to cities in search of employment. According to a report compiled by the University of Michigan, the percentage of the world's population living in cities in 1950 was less than 30%, and in 2000 the figure rose to 47%. The study predicts that by 2025, this figure will reach 60% (World watch, 2011). Rapid migration is the result of factors that induce migration from rural to urban areas; These factors have been classified into two broad groups: push and pull factors. Push factors are those factors that are influenced by the conditions of rural areas, thereby pushing people to migrate to cities. Pull factors, on the other hand, are the incentives that attract people to cities. Examples of push factors can be political instability of the rural area, insecurity, low education level, unemployment and scarcity of resources. Pull factors are the promise of what is lacking in rural areas: employment, better education, a better lifestyle, a variety of resources, better health facilities and some political stability... middle of paper..... "Urbanization and megacities: the need for spatial information management". FIG REPORT Publication No. 48, January 2010. Retrieved March 9, 2011 from www.fig.net/pub/figpub/pub48/figpub48.pdf*University of Michigan, “Urbanization and Global Change,” April 1, 2006. Accessed 1 April 2006. March 9, 2011 at http://www.globalchange.umich.edu/globalchange2/current/lectures/urban_gc/*WORLDWATCH INSTITUTE. “Rapid urbanization draws attention from experts.” Vision for a Sustainable World, March 9, 2011. Retrieved March 9, 2011 from http://www.worldwatch.org/node/64*Zhou, Hongjian et al. “Rapid urbanization and implications for the restoration of river ecological services: a case study in Shenzhen, China.” » Journal of urban planning and development: 10.1061. Retrieved March 9, 2011, from http://ascelibrary.org/upo/resource/3/jupdxx/33