Final answer:
Japan has a population density nearly ten times that of the United States, being 899 persons per square mile compared to the U.S.'s 92. The high density in Japan is due to urban concentration in coastal areas and low birth rates leading to a declining population.
Step-by-step explanation:
In 2017, the population density of Japan was 899 persons per square mile which is nearly ten times as densely populated as the United States, with its population density of 92 persons per square mile. This disparity can be attributed to Japan's geographical constraints and urban planning, with a substantial portion of its population living in highly urbanized areas along the coast, particularly in the area extending from Tokyo to Nagasaki.
Japan's population trends are influenced by several factors including a low birth rate, with an average of about 1.2 children per family, and a rising aging population due to high personal incomes and a highly urban and industrial society. These demographic trends present challenges for Japan including a declining population and a lack of youth to take on entry-level jobs.