During the Industrial Era, there was a growth spurt worldwide. The development of factories brought people from rural to urban areas, and new technology increased the efficiency of transportation, food production, and food preservation. For example, from the mid-1670s to the early 1900s, London’s population increased from 550,000 to 7 million. Global favorites like New York, London, and Tokyo are all examples of postindustrial cities. As cities evolve from manufacturing-based industrial to service- and information-based postindustrial societies, gentrification becomes more common. Gentrification occurs when members of the middle and upper classes enter and renovate city areas that have been historically less affluent while the poor urban underclass are forced by resulting price pressures to leave those neighborhoods for increasingly decaying portions of the city.
Globally, 55 percent of the world’s people currently reside in urban areas, with the most urbanized region being North America (82 percent), followed by Latin America/the Caribbean (81 percent), with Europe coming in third (74 percent). In comparison, Africa is only 40 percent urbanized, though one of its nations, Nigeria, is projected to significantly urbanize in the coming years. With 37 million people, Tokyo is the world’s largest city by population, and New Delhi is the second largest with 29 million. The world’s most densely populated cities are now largely concentrated in the global south, a marked change from several decades ago when the biggest cities were found in the global north. In the next forty years, the biggest global challenge for urbanized populations, particularly in less developed countries, will be to achieve development that occurs without depleting or damaging the natural environment, also called sustainable development.