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Figure 7.1 to see how one end of the spectrum contains Japan’s land area is 145,936 square miles (377,974
densely settled areas having more than 250 persons per square kilometers), and its mid-2018 population was
square mile (97 or more per square kilometer). At the 126.5 million. We calculate Japan’s arithmetic density
other end of the spectrum, largely unpopulated areas by dividing its population by its land area, or 126.5
have fewer than 2 persons per square mile (less than million ÷ 145,936 square miles, which yields 867 peo-
1 per square kilometer). Between these two extremes ple per square mile (335 people per square kilometer).
are moderately settled areas, with 60 to 250 persons per This is certainly a fairly high density when we con-
square mile (25 to 100 per square kilometer), and thinly sider that the arithmetic density of the United States
settled areas, inhabited by 3 to 59 persons per square is just one-tenth of that. But it is physiological den-
mile (2 to 24 per square kilometer). Country-level pop- sity that conveys the crowdedness that has defined
ulation density varies a great deal too. For example, the Japanese psyche and Japanese people’s daily life.
Australia has only 8 persons per square mile (3 per Only 11.7 percent of Japan’s land, or 17,074.51 square
square kilometer), but Bangladesh has 2927 persons miles, is arable. Dividing Japan’s total population by
per square mile (1130 per square kilometer). its arable land area yields a physiological density of
Arithmetic density can be misleading because it 7409 people per square mile, compared to about 550
masks the considerable geographic variation in pop- people per square mile for the United States. Similarly,
ulation density within a country. That is, arithmetic Egypt’s arithmetic density is 249 people per square
density does not reflect how the population is actually mile, but its physiological density is 8881 people per
distributed. Assume there are two countries of the same square mile because less than 3 percent of Egypt’s
size and population. Country A is very mountainous, so land is suitable for farming (Figure 7.11).
its residents are concentrated in a few narrow coastal
plains. Country B is much flatter, so its population
is more evenly spread out. Both countries have the
same arithmetic density, which might falsely suggest
that these countries’ inhabitants are evenly distrib-
uted across their land area. However, the residents of
Country A are likely to feel far more crowded because
they are concentrated in a small inhabitable area.

Physiological Density

To mitigate the drawbacks associated with arithme-
tic density, geographers use another density measure
called physiological density, which is the average num-
ber of people per unit area (a square mile or kilometer)
of arable land — that is, land suitable for cultivation. We
calculate physiological density by dividing a country’s
population by the amount of its arable land. Again, the
higher the number, the more crowded a country is.
In countries with a significant portion of land that
cannot be used to grow crops (deserts, mountains,
water bodies, swamps), physiological density will be
much higher than arithmetic density. For example,

TERMS TO KNOW . . .

physiological density: The average number of people Figure 7.11 The Nile River Valley. Less than three percent of
per unit area (a square mile or kilometer) of arable land Egypt’s land is suitable for farming, mostly along the Nile River.
On this satellite image, the Nile River and its delta are clearly
arable land: Land suitable for cultivation visible. World History Archive / Alamy Stock Photo

16 Unit 2 Population and Migration Patterns and Process
©2021 BFW Publishers. Sample material is NOT FINAL and corrections will be made prior to publication.

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