The increase in the proportion of a population living in urban areas and the process by which an area loses its rural character and way of life. Urbanization is a consequence mainly of rural-urban migration. This process began in Europe in the 19th century. Although large cities existed before 1800, the vast majority of the world's population lived in small, often self-sufficient village communities. Industrialization and population growth in Europe in the 19th century resulted in radical change: sometimes the excess peasant population moved to towns to seek paid work, often having to live in unhygienic slums and dying of infectious diseases.
Urbanization in the 20th century has proceeded at an unprecedented rate. In 1900 the UK became the first country to be predominantly urban. In 1920 only about 14% of the world's population lived in urban areas but by 1950 the proportion had reached 25% and by 1990, 43%. The transport revolution has ensured that many villages near large cities in Western Europe or the USA have become little more than dormitories for urban workers, who commute daily to the city. If present trends continue, some 60% of the world's population could be living in towns and cities by 2025.