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CHAPTER 5: Processes and Cycles of Population Change (De Blij & Murphy)

Population Notes

CHAPTER 5:  Processes and Cycles of Population Change


1)  The population explosion of the past 200 years has increased from 1 billion to 6 billion.

2)  Although hundreds of millions remain inadequately nourished, the threat of global hunger has receded – perhaps temporarily.

3)  Rapid population growth varies over time and space. 

4)  Keys to reduction of population growth rates include providing greater access to education for women and securing their rights in society.

5)  The demographic transition model suggests that the world's population will stabilize in the twenty-first century, but the model may not be universally acceptable.

I)  Worldwide Population Trends

A)    World Growth Rate

         1)  Adding about 80 million people every year; most increase is in areas that are least able to support new arrivals

         2)  Growth rate of world's population declined from 2.1% per year during 1965-69 to 1.6% during 1985-89. (Today = ~1.4%)

         3)  Even while global population growth rate has continued to decline, the reduction has been offset by the even larger total on which it is based.

         4)  Fastest growth in Subsaharan Africa, South Asia & Muslim countries.  Smallest in Europe , N. America , Russia & Japan .

II)     Dimensions of Population Growth

A)     Arithmetic (linear) Growth

1)       Increases occur in uniform amounts.

2)       Human population has not expanded in a linear manner.

B)      Exponential Growth

1)       Cumulative or compound growth over a period of time.

2)       Human population increases this way.

C)      Doubling time (70/rate of increase)

1)       The time required for a population to double in size.

2)       Rates of Population Growth and Doubling Time:

Rate of Increase (%)

Doubling Time (yrs.)

Example (1998)









Costa Rica




3)       Population Explosion

a)       History of humanity is one of growing numbers and even higher rates of increase

b)       2000 yrs. ago – 250 million: doubling time 16 centuries (1650)

c)       1650 – 500 million: doubling time 170 yrs. (1820) …

d)      2000 – doubling time reduced to 35 yrs. (>6 billion currently)

D)     Stabilizing Population Level (SPL)

1)       Theory that populations will stop growing (e.g. some Western European nations)

2)       Population increase is a cyclic phenomenon – lags, spurts, regional disparities

III)   Population Theories

A)     Malthusian

1)       1798 – Thomas Malthus claims population increasing faster (geometric) than food production (arithmentic)

2)       Did not foresee colonization, migration, Green Revolution, …

B)      Boserupian

1)       Technology will increase food production, counterbalance population increase

C)      Cornucopian

1)       Plenty of natural resources and food, world cannot become overcrowded

IV)   Population Structures

A)     Graphic representation (profile) of a population according to age and sex.

B)      Age-Sex Pyramid – shows population composition (structure)

1)       Graphic representation (profile) of a population showing the percentages of the total population by age and sex, normally in five-year groups (cohorts)

2)       Sexes are placed on the left (males) and the right (females)

3)       Broad bases = high fertility and mortality rates

4)       Narrower bases = lower fertility and mortality rates

Source: United Nations, World Population Prospects, The 1998 Revision.

V)     Demographic Cycles

A)     Natural Increase = Crude Birth Rate (CBR) – Crude Death Rate (CDR)

1)       CBR – not solely related to economic condition (e.g. poor countries have high birth rates)

2)       CDR – (a.k.a. mortality rate) includes infant mortality (increases the rate)

B)      Total Fertility Rate (TFR)

1)       Number of children born to women of childbearing age

2)       TFR usually reported as number of children per woman

3)       Generally, the age at which a woman first marries is directly related to the number of children she will bear because it affects the length of time she will be at risk of becoming pregnant.

4)       Access to contraception is an important contributor to the differences in the fertility rates among countries, but culture and socioeconomics weigh heavily as well.

C)      Population Changes

1)       Limits on Population

a)       Epidemics, plagues (e.g. 1348-50 Europe affected by bubonic plague)

b)       Famines (e.g. 18th & 19th c. India and China – millions died)

c)       Wars (e.g. World Wars I & II)

2)       Second Agricultural Revolution & Industrial Revolution

a)       Farming methods improve, crop yields increase, improved storage capacities

b)       Improved sanitation facilities, medical advancements (e.g. vaccination)

c)       Increased migration – leads to colonization (widespread epidemics)

VI)               Demographic Change

A)     TP = OP + B – D + I – E; takes immigration and emigration into account  

B)      Demographic Transition (Cycle)

1)       Four Stages:

a)        High stationary stage – high fertility and mortality, variable population, little long-term growth

b)       Early expanding stage – high fertility, declining mortality

c)       Late expanding stage – declining fertility, but as a result of already-low mortality, continuing significant growth

d)      Low stationary stage – low fertility and mortality, very low rate of growth

chart 2A

2)       Based on the European model (e.g. United Kingdom , birth rate declined due to industrialization, urbanization, modernization).  Unwise to assume all countries’ demographic cycles will follow UK ’s path.

3)       Developing countries

a)       Population base is larger,

b)       Affected by 1st world nations

c)       Signs that population “bomb” may be declining