Final answer:
The largest contributing factor to increased urbanization is migration. Urbanization is fueled by the movement of people from rural to urban areas, attracted by better opportunities and economic factors such as industrialization, technological growth, and service sector expansion.
Step-by-step explanation:
Urbanization has been a defining trend of recent centuries, as economies transition from agrarian-based to industrial and service-oriented. The explosion of urbanization is primarily due to migration, with individuals and families moving from rural to urban areas in search of better employment opportunities, education, and lifestyle options. This rural-to-urban shift has been bolstered by economic factors such as industrialization, technological advancements, and the growth of the service sector. Additionally, as nations develop, urban areas expand due to agglomeration factors, which describe the benefits obtained when firms and people come together in a centralized location, including shared services, infrastructure, and markets.
Throughout the 20th century and into the 21st, this migration trend has led to a significant growth of urban populations worldwide. In the United States, for instance, there was a considerable shift from rural to urban areas, with about 80% of the population now living in metropolitan areas, a stark increase from the 40% in 1900. However, the management and sustainability of this urban growth present enormous challenges, especially for developing nations where urban infrastructure may not be well-equipped to handle the rapid increase in population.