Urbanization is the physical growth of urban areas into rural as a result of population in- migration to an existing urban area.
Urbanization refers to a process in which an increasing proportion of an entire population lives in cities and the suburbs of cities. Historically, it has been closely connected with industrialization. When more and more inanimate sources of energy were used to enhance human productivity (industrialization), surpluses increased in both agriculture and industry.
Larger and larger proportions of a population could live in cities. Economic forces were such that cities became the ideal places to locate factories and their workers.
Effects include change in density and administration services. While the exact definition and population size of urbanized areas varies among different countries, urbanization is attributed to growth of cities.
Urbanization is also defined by the United Nations as movement of people from rural to urban areas with population growth equating to urban migration. The UN projects half the world population will live in urban areas at the end of 2008.
The 2005 Revision of the UN World Urbanization Prospects report described the 20th century as witnessing “the rapid urbanization of the world’s population”, as the global proportion of urban population rose dramatically from 13% (220 million) in 1900, to 29% (732 million) in 1950, to 49% (3.2 billion) in 2005. The same report projected that the figure is likely to rise to 60% (4.9 billion) by 2030.
Urbanization rates vary across the world. The United States and United Kingdom have a far higher urbanization level than China and India, but a far slower annual urbanization rate, since much less of the population is living in a rural area.