Today, the majority of the world’s population lives in an urban setting. This may be in the form of small towns of a few thousand people, or megacities and metropolises with tens of millions of inhabitants. However, large scale urbanization is a relatively new phenomenon for humanity, and the movement of populations from a rural to urban setting generally corresponds with a society’s industrial development. Pre-industrial urbanization Throughout most of human history, families generally built their own homes and were dependent on subsistence agriculture (i.e. growing their own food); because of the threat of food instability, and the labor demands of subsistence farming, this meant that fewer than 5-10 percent of the total population lived in towns or cities. Urban areas in pre-industrial times were generally trade or administrative centers, although there were some larger areas with relatively dense populations – this included Mesopotamia (present-day Iraq and Syria) or the Nile Delta (Egypt) before the Common Era, or the proto-industrial areas of Flanders and Northern Italy during the medieval period. As European imperial expansion grew from the 15 th century, cities also developed around these trade routes and with the discovery of rich resource deposits , but it was not until the industrial revolution where modern urbanization trends developed. Industrial urbanization Throughout the 18 th century, the efficiency and output of Britain’s agricultural sector improved greatly; the gradual decline of agriculture’s labor demand eventually led to millions of people flocking to cities in search of employment in the emerging industrial sector. Between 1800 and 1890, the share of the urban population rose from 20 to 62 percent in England and Wales . Similar trends also occurred across Belgium, France , and Germany , albeit at a slower pace. The shift in Europe’s agricultural employment also saw millions of rural Europeans migrate across the Atlantic ; the most common point of arrival was the Northeastern U.S., where industrialization and urbanization rates were fastest (a decisive factor in the Union’s victory in the American Civil War ). At the turn of the 20 th century, urbanization in Brazil, Japan, Oceania, Russia, and Southern Europe also rose during the Second Industrial Revolution, but still lagged behind the most advanced societies. The spread of communism and command economies in the middle of the 20 th century saw urbanization develop differently in Eastern Europe and parts of Asia, but with mixed results, as mismanaged attempts to accelerate industrialization and collectivize farming often led to food shortages; the most extreme cases of these resulted in man-made famines that killed millions in both the Soviet Ukraine and China. In global terms, the world population experienced its most rapid urbanization since the Second World War, as much of East Asia and Latin America underwent significant industrial development and population growth. Post-industrial urbanization The concentration of the world population in Asia has meant that this region has a disproportionate effect on global averages; over half of the world’s population lives in the region between Pakistan, Japan, and Indonesia, and 13 of the world’s 20 largest cities are found here . As South and Southeast Asia continue to urbanize in the coming years this will bring the global average higher, at a faster rate than Europe in centuries past. Africa’s development, however, will likely have the largest impact on future development – the population of Africa is expected to grow by three billion people by the end of this century. In contrast to previous centuries, where employment moved from agriculture to manufacturing, current trends show a higher number of people moving directly into service industries . In Africa, the s ervice sector already employs over 40 percent of the working population, and this will likely overtake agricultural employment in the next years. Urbanization: opportunities and challenges There are many positive and negative aspects associated with urbanization; many of these factors can vary from one town or city to the next and are susceptible to the economic development of a society. For individuals, urban life can offer greater or more diverse opportunities in employment, social relationships, and recreation, however it may also be more expensive, stressful , or alienating than life in a rural community. Health is another area that varies greatly by location; cities offer greater access to healthcare , but pollution, sedentary lifestyles, and exposure to disease can present adverse health risks. Administratively, urban planning is one of the primary functions of government, and the need to provide adequate sanitation, transport , and infrastructure for larger populations requires significant investment to maintain high living standards. Urban planning is also required to reduce the environmental impact of urbanization, not just from carbon emissions , but also aspects such as encroachment onto natural habitat and water pollution . Understanding urbanization The process of urbanization is the movement of populations from rural to urban areas, and urbanization rates refer to the share of the population living in built up areas. Disparities in urbanization statistics may cause confusion as methodologies vary by country, and create problems when comparing countries' urbanization rates. For example, Sweden defines an urban area as having at least 200 inhabitants, while this figure is 2,500 in the U.S., and 50,000 in Japan (alongside other criteria). Additionally, urbanization is sometimes confused with population density , which is the average number of people per unit area (e.g. population per km²) - these both deal with geographical population distribution, but do not always correlate - for example, Iceland is one of the highest urbanized countries in the world, but also one of the lowest population densities, due to the concentration of the population around the capital . This text provides general information.