Page 55 - bfw-APHG-1e

double in 233 years. However, this number does not We began this Module by describing the impres-
account for the relatively high levels of immigration to sive growth of the world’s human population. There are
the United States, which will cause its population to three basic components of population dynamics: births,
double in a shorter period of time. deaths, and migration. We explained how to measure
For an example of a country with higher rates of pop- births, deaths, and natural increase, and we exam-
ulation growth, let’s consider Nigeria again. Because its ined the global patterns of the key measures. We will
population is growing at 2.6 percent per year, Nigeria’s cover migration in the last three Modules of this Unit.
population will double in just 27 (= 70 ÷ 2.6) years, faster Worldwide, birth rates and death rates have been on
than many other countries. This increase explains why a downward trend, but considerable geographic differ-
Nigeria is likely to become the world’s third most populous ences remain, particularly in birth rates, which are in
country, just after India and China, by the mid-twenty- turn shaping variations in the rate of natural increase.
first century. The doubling of Nigeria’s population means The concepts covered in this Module provide a foun-
that the country must provide health care, education, dation for understanding later Modules on the demo-
jobs, fresh water, and housing for twice as many people graphic transition model, Thomas Malthus’s theory of
27 years from now. This challenge is quite daunting. population, and government population policies.

Module 9 Review

9-1
Ho
w has the w
tion g
9-1 How has the world’s population grown influences, education, gender roles, and population
r
o
orld
wn
s popula
’
over time?
over time? policies.
• Human population remained small for a long
time, but grew exponentially after the Industrial 9-3 Ho w do w e measur e dea th r a t es?
How do we measure death rates?
9-3
Revolution in the mid-eighteenth century, doubling
in shorter and shorter periods of time. The growth • Crude death rate (CDR), or mortality rate, is the
has slowed in recent times. number of deaths per year per 1000 people. The
• Total world population is expected to reach 11.2 world’s CDR in 2018 was 7 deaths per 1000 people.
billion by 2100, based on the future estimated fertil- More-developed countries have slightly higher death
ity rate being medium, or at the replacement level, rates than less-developed countries because their
from today’s 7.76 billion. populations are older.
• Much of the future population growth will take place • Infant mortality rate (IMR) measures how many
in developing countries, especially sub-Saharan infants die in their first year per 1000 live births.
African countries. It is considered the best single indicator of living
standards. The world’s IMR is 31. Most developed
a
Ho
e measur
e bir
w do w
9-2 How do we measure birth rates? countries have a low single-digit IMR, but develop-
es?
9-2
th r
t
ing countries’ IMRs may be as high as 50–70.
• One method is the crude birth rate (CBR), or the
average number of births per 1000 people. The
world’s average CBR in 2018 was 19 per 1000 popu- 9-4 How do we measure natural increase?
tur
ease?
al incr
9-4
w do w
Ho
e measur
e na
lation, with developed countries having lower rates
and developing countries having higher rates. • Natural increase in population refers to the differ-
• Another method is the total fertility rate (TFR), ence between total births and deaths in a given year.
which is the average number of children born per It is usually expressed as a percentage of total popu-
woman during her reproductive lifetime. A TFR of lation, or the rate of natural increase (RNI).
2.1 is replacement level fertility, necessary to replace • When birth rate equals death rate, a country reaches
both parents. zero population growth. There is no natural increase
• Fertility rates are affected by several factors, includ- in population (i.e., RNI = 0), but age and sex structure
ing economic development, religious and cultural may still change.
44 Unit 2 Population and Migration Patterns and Process
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