Final answer:
About 80% of the population increase each year occurs in the cities of less-developed countries.
Step-by-step explanation:
About 80% of the population increase each year occurs in the cities of less-developed countries. This can be seen from the information provided that the proportion of the population living in urban areas in poorer nations, including much of Africa, is about 30% compared to about 80% in the United States. As economies develop, there is an increasing proportion of the population living in urban areas.