Final answer:
The percentage of the population living in urban areas is increasing everywhere, with high-income and poorer nations alike experiencing urban growth. Middle-income countries are also witnessing significant rural-to-urban migration.
Step-by-step explanation:
The percentage of the population living in urban areas is increasing everywhere. Reports indicate that urbanization is occurring in all economic brackets: high-income countries such as the United States have seen their urban population grow from 40% in 1900 to about 80% now, while in poorer nations, the urban population, although starting from a much lower base, is also growing. For instance, in African countries, typically low-income, approximately 30% of the population resides in urban areas, which signifies an increase and highlights the challenges they face in managing the growth of cities as their economies develop.
In middle-income countries, there is a substantial rural-to-urban shift, with cities like Mumbai advancing into the latter stages of the urbanization index, resulting in smaller family sizes and predictions of population stabilization. Everywhere, as nations develop economically, there's a consistent trend of increasing urbanization, directly linked to income levels and the structural transformation of their economies.