Urbanization, urbanisation (see spelling differences) or urban drift is the physical growth of urban areas as a result of rural migration and even suburban concentration into cities, particularly the very largest ones. The United Nations projected that half of the world's population would live in urban areas at the end of 2008.[1] Urbanization is closely linked to modernisation, industrialisation, and the sociological process of rationalisation. Urbanisation can describe a specific condition at a set time, i.e. the proportion of total population or area in cities or towns, or the term can describe the increase of this proportion over time. So the term urbanisation can represent the level of urban relative to overall population, or it can represent the rate at which the urban proportion is increasing. Urbanisation is not merely a modern phenomenon, but a rapid and historic transformation of human social roots on a global scale, whereby predominantly village culture is being rapidly replaced by predominantly urban culture. The last major change in settlement patterns was the accumulation of hunter-gatherers into villages many thousand years ago. Village culture is characterised by common bloodlines, intimate relationships, and communal behavior whereas urban culture is characterised by distant bloodlines, unfamiliar relations, and competitive behavior. This unprecedented movement of people is forecast to continue and intensify in the next few decades, mushrooming cities to sizes incomprehensible only a century ago. Indeed, today, in Asia the urban agglomerations of Dhaka, Karachi, Mumbai, Delhi, Manila, Seoul and Beijing are each already home to over 20 million people, while the Pearl River Delta, Shanghai-Suzhou and Tokyo are forecast to approach or exceed 40 million people each within the coming decade. Outside Asia, Mexico City, Sao Paulo, New York City, Lagos and Cairo are fast approaching or home to over 20 million people already.

As more and more people leave villages and farms to live in cities, urban growth results. The rapid growth of cities like Chicago in the late 19th century, Tokyo in the mid twentieth, and Mumbai in the 21st century can be attributed largely to rural-urban migration. This kind of growth is especially commonplace in developing countries. This phenomenal growth can also be attributed to the lure of not just economic opportunities, but also to loss or degradation of farmland and pastureland due to development, pollution, land grabs, or conflict, the attraction and anonymity of hedonistic pleasures of urban areas, proximity and ease of mass transport, as well as the opportunity to assert individualism. 'Urbanization is not about simply increasing the number of urban residents or expanding the area of cities. More importantly, it’s about a complete change from rural to urban style in terms of industry structure, employment, living environment and social security.' Li Keqiang, Premier-elect of China[2] The rapid urbanization of the world’s population over the twentieth century is described in the 2005 Revision of the UN World Urbanization Prospects report. 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.[3] Percentage of World Population: Urban vs. Rural.[4] According to the UN State of the World Population 2007 report, sometime in the middle of 2007, the majority of people worldwide will be living in towns or cities, for the first time in history; this is referred to as the arrival of the "Urban Millennium" or the 'tipping point'. In regard to future trends, it is estimated 93% of urban growth will occur in developing nations, with 80% of urban growth occurring in Asia and Africa.[5][6] Urbanization rates vary between countries. The United States and United Kingdom have a far higher urbanization level than China, India, Swaziland or Niger, but a far slower annual urbanization rate, since much less of the population is living in a rural area. Some nations make a distinction between suburban and urban areas, while others do not, indeed, human conditions within such areas differ greatly. Urbanization in the United States never reached the Rocky Mountains in locations such as Jackson Hole, Wyoming; Telluride, Colorado; Taos, New Mexico; Douglas County, Colorado and Aspen, Colorado. The state of Vermont has also been affected, as has the coast of Florida, the Birmingham-Jefferson County, AL area, the Pacific Northwest and the barrier islands of North Carolina. In the United Kingdom, two major examples of new urbanization can be seen in Swindon, Wiltshire and Milton Keynes, Buckinghamshire.[7] These two towns show some of the quickest growth rates in Europe. Urbanization in Makati, Philippines Urbanization occurs as individual, commercial, and governmental efforts to reduce time and expense in commuting and transportation while improving opportunities for jobs, education, housing, and transportation. Living in cities permits the advantages of the opportunities of proximity, diversity, and marketplace competition. However, the advantages of urbanisation are weighed against alienation issues, stress, increased daily life costs, and negative social aspects that result from mass marginalisation. Suburbanisation, which is happening in the cities of the largest developing countries, was sold and seen as an attempt to balance these negative aspects of urban life while still allowing access to the large extent of shared resources. Cities are known to be places where money, services and wealth are centralised. Many rural inhabitants come to the city for reasons of seeking fortunes and social mobility. Businesses, which provide jobs and exchange capital are more concentrated in urban areas. Whether the source is trade or tourism, it is also through the ports or banking systems that foreign money flows into a country, commonly located in cities. Economic opportunities are just one reason people move into cities, though they do not go to fully explain why urbanisation rates have exploded only recently in places like China and India. Rural flight is a contributing factor to urbanisation. In rural areas, often on small family farms or collective farms in villages, it has traditionally been difficult to access manufactured goods, though overall quality of life is very subjective, and may certainly surpass that of the city. Farm living has always been susceptible to unpredictable environmental conditions, and in times of drought, flood or pestilence, survival may become extremely problematic. In a New York Times article concerning the acute migration away from farming in Thailand, life as a farmer was described as "hot and exhausting." "Everyone says the farmer works the hardest but gets the least amount of money".[10] In an effort to counter this impression, the Agriculture Department of Thailand is seeking to promote the impression that farming is “honorable and secure.”[11] However, in Thailand, urbanization has also resulted in massive increases in problems such as obesity. City life, especially in modern urban slums of the developing world, are certainly hardly immune to pestilence nor climatic disturbances such as floods, yet continue to strongly attract migrants. Examples of this were the 2011 Thailand floods and 2007 Jakarta flood. Urban areas are also far more prone to violence, drugs, and other urban social problems. In the case of the United States, industrialisation of agriculture has negatively affected the economy of small and middle-sized farms and strongly reduced the size of the rural labor market. These are the costs of participating in the urban economy. Your increased income is canceled out by increased expenditure. In the end, you have even less left for food. —Madhura Swaminathan, economist at Kolkata’s Indian Statistical Institute[12] Particularly in the developing world, conflict over land rights due to the effects of globalisation has led to less political powerful groups, such as farmers, losing or forfeiting their land, resulting in obligatory migration into cities. In China, where land acquisition measures are forceful, there has been far more extensive and rapid urbanisation (51%) than in India (29%), where peasants form militant groups (e.g. Naxalites) to oppose such efforts. Obligatory and unplanned migration often results in rapid growth of slums. This is also similar to areas of violent conflict, where people are driven off their land due to violence. Bogota, Colombia is one example of this. Cities offer a larger variety of services, such as specialist services that aren't found in rural areas. Supporting the provision of these services requires workers, resulting in more numerous and varied job opportunities. Elderly individuals may be forced to move to cities where there are doctors and hospitals that can cater for their health needs. Varied and high quality educational opportunities are another factor in urban migration, as well as the opportunity to join, develop, and seek out social communities.