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Difficulty: Very hardPopulation Distribution, Density, and Migration in Africa

In a demographic study of an agricultural region in West Africa covering a total surface area of 150000 km2150{}000\text{ km}^2 (20%20\% of which consists of non-arable mountainous terrain and water bodies), the population at the beginning of a 10-year census period was 90000009{}000{}000. Over the 10-year period, official demographic records indicate 27000002{}700{}000 live births, 10500001{}050{}000 deaths, 600000600{}000 inbound immigrants, and 150000150{}000 outbound emigrants. What is the physiological population density of the region in persons per square kilometer of arable land at the end of the 10-year period?

Answer: 92.5 persons/km²

Answer

92.5 persons per square kilometer of arable land
To calculate the physiological population density, the final population must be divided strictly by the area of arable land. The total ending population is obtained by taking the initial population (90000009{}000{}000), adding natural increase (2700000−1050000=16500002{}700{}000 - 1{}050{}000 = 1{}650{}000), and adding net migration (600000−150000=450000600{}000 - 150{}000 = 450{}000), which gives 1110000011{}100{}000 persons. The arable land area is 80%80\% of 150000 km2=120000 km2150{}000\text{ km}^2 = 120{}000\text{ km}^2. Dividing 1110000011{}100{}000 by 120000120{}000 yields 92.5 persons/km292.5\text{ persons/km}^2.

Step-by-Step Solution

1
Calculate the area of arable land
Arable land area = 150000 km2×(1−0.20)=120000 km2150{}000\text{ km}^2 \times (1 - 0.20) = 120{}000\text{ km}^2
Physiological population density measures population relative to arable (cultivable) land only, excluding non-arable terrain.
2
Calculate the natural population increase
Natural Increase = 2700000 births−1050000 deaths=1650000 persons2{}700{}000\text{ births} - 1{}050{}000\text{ deaths} = 1{}650{}000\text{ persons}
Natural population change is the net difference between live births and deaths.
3
Calculate net migration
Net Migration = 600000 immigrants−150000 emigrants=450000 persons600{}000\text{ immigrants} - 150{}000\text{ emigrants} = 450{}000\text{ persons}
Net migration accounts for population change caused by movement into and out of the region.
4
Determine final total population
Final Population = 9000000+1650000+450000=11100000 persons9{}000{}000 + 1{}650{}000 + 450{}000 = 11{}100{}000\text{ persons}
Total population at the end of the period equals initial population plus natural increase plus net migration.
5
Calculate physiological population density
Physiological Density = 11100000 persons120000 km2=92.5 persons/km2\frac{11{}100{}000\text{ persons}}{120{}000\text{ km}^2} = 92.5\text{ persons/km}^2
Physiological density is computed by dividing the total ending population by the arable land area.

Key Concept

Physiological Population Density and Net Population Change
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Topics

Population Distribution, Density, and Migration in Africa

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