chapter 11 human population: growth & distribution © brooks/cole publishing company / itp

Chapter 11Chapter 11Human Population:Human Population:

Growth & DistributionGrowth & Distribution

© Brooks/Cole Publishing Company / ITP

OutlineOutline

1. Factors Affecting Human Population Sizebirth & death rates

2. Population Age Structureage structure diagrams, developing vs. developed countries

3. Solutions: Stabilizing Human Populationcomputer models, demographic transition

4. Case StudiesUnited States, India, China

5. Human Population & Sustainability


Human Population Growth

How would you describe the population before 1700?


How would you describe the population after 1700?


What kinds of historical events were taking place in the 1700s and 1800s?


How has the amount of time it takes for the population to grow by 1 billion changed?


Population Year Reached Years to Reach

1 billion 1850 Tens of thousands

2 billion 1930 80

3 billion 1960 30

4 billion 1974 14

5 billion 1987 13

6 billion 1999 12

Factors Affecting Human Population SizeFactors Affecting Human Population Size


Human population is currently growing exponentially:

• What will be the ultimate size of the human population?

• What is Earth's carrying capacity? (How many humans can Earth support?)

Factors Affecting Human Population SizeFactors Affecting Human Population Size


Population ChangeBirths

+Immigration

Deaths+

Emigration–=

Population change is calculated as the difference between individuals entering and leaving a population:

• Birth rate – is the number of births per thousand people

• Death rate – is the number of deaths per thousand people

• Zero population growth (ZPG) occurs when factors that increase and decrease population size balance

Crude Birth & Death RatesCrude Birth & Death Rates


Developed countries tend to have lower birth rates & death rates than developing countries.

Why?

Population ChangePopulation Change


The annual rate of population increase is generally expressed as a percentage.

What information can you gather from this map?

Population Size by ContinentPopulation Size by Continent


Population size by region in 1998, with projections of population size in 2025.

There are about 84 million births each year.

(97% of new births are in developing countries)

Birth & Death Rates Over TimeBirth & Death Rates Over Time


In developed countries, decreases in death rates are being accompanied by decreases in birth rates over time.



In developing countries, decreases in death rates have not been accompanied by as large of decreases in birth rates over time, leading to major population increase.

Population SizePopulation SizeFertility RatesFertility Rates


Measure of the number of children that will be born

1) Replacement Fertility - Number of children needed to replace the parents (2.1 in developed countries, 2.5 in some developing countries)

2) Total Fertility Rate (TFR) - Average number of children each woman has in a population

Average TFR (births per woman)2.8 - Developing Countries

2.4 - Middle Income Countries1.7 - Upper Income Countries

Total Fertility in the United StatesTotal Fertility in the United States


Total fertility in the United States had a major increase during the "baby boom" (1946–1964) & is now hovering just below replacement level.

Factors Affecting Fertility RatesFactors Affecting Fertility Rates


What factors decrease human fertility levels?

What causes people to have fewer children?

You rocket.How do you get a baby

astronaut to fall asleep?

Factors Affecting Fertility RatesFactors Affecting Fertility Rates


The following are significant factors that decrease human fertility levels:• increase in average level of education & affluence• decrease in importance of child labor• increased urbanization• increased cost of raising & educating children• increased educational & employment opportunities for women• decreased infant mortality• higher average age of marriage• greater availability of private & public pensions• greater availability of reliable birth control• greater availability of legal abortions• change in religious beliefs, traditions, & cultural norms away

from encouraging large families

TFR (births per woman)

Teen Pregnancy

• Which industrialized country has the highest teenage pregnancy rate?

• How many teenage girls become pregnant each year?

• What percentage of those pregnancies were unplanned?

872,000

The United States

78%

Birth ControlBirth Control


Typical effectiveness of birth control methods in the United States:

Birth ControlBirth Control


Typical effectiveness of birth control methods in the United States (continued):

Death RatesDeath Rates


“It’s not as if people suddenly started breeding like rabbits; it’s just that they stopped dying like flies.” Peter Adamson

Life expectancy - The number of years a newborn can expect to live.

Developing Countries - 64.6 years

Middle Income Countries - 69.6 years

Upper income Countries - 78.2 years



“It’s not as if people suddenly started breeding like rabbits; it’s just that they stopped dying like flies.” Peter Adamson

Infant mortality - Number of babies out of every 1,000 that die within a year of birth

Angola – 182.3

India – 32.3

United States – 6.3

Singapore – 2.3

World Average – 42.1

Infant Mortality Rate vs. GDP



Infant death rates are lower in developed countries than developing countries



The rapid growth in the world's population has not resulted from an increase in birth rates, but rather a major decrease in death rates.

• death rates have decreased markedly during the past 100 years

• birth rates have also decreased, but not as fast as death rates

• the increasing difference between birth & death rates is what has lead to exponential population growth

• the patterns of change in birth & death rates over time are different for developed vs. developing countries

Think About It

• Which age group do you think has the biggest population in Chester County?

Chester County, PA

Population Age StructurePopulation Age Structure


Age structure refers to the proportion of the population in each age class:

• prereproductive (0–14 years)

• reproductive (15–44 years)

• postreproductive (45 & up)



Age structure of a rapidly growing vs. a slower growing population.

Rapidly growing populations have pyramid–shaped age structures, with large numbers of prereproductive individuals. Slower growing populations have a more even age distribution.



Age structure of populations with zero growth vs. negative growth.

Populations with zero population growth have nearly equal proportions of prereproductive & reproductive individuals; whereas populations with negative growth have a greater proportion of reproductive than prereproductive individuals.



Population age structure of the United States continues to show a bulge as the “baby boom” generation ages. This has been compared to watching a boa constrictor swallow a pig.

Matching Review

A. Rapid GrowthB. Zero Growth

C. Negative GrowthD. Slow Growth

B C A D

Demographic Demographic IndicatorsIndicators


Fig.11–15



Developing countries are expected to continue to have a pyramid shape through the year 2025, although the age structure will become somewhat more evenly distributed.

Fig.11–14a



Populations of developed countries are expected to have an increasingly even age distribution through the year 2025.

Fig.11–14b

Developed vs. Developing

Demographic TransitionDemographic Transition


A generalized model of demographic transition (four stages):



1) Preindustrial Stage:

• Birth rate and death rates are high & approximately equal

• population does not increase

• population size is smallBirth rate

Death rate

Total pop.



2) Transitional Stage:

• death rate decreases because of industrialization, increased food production, & improved health care

• birth rate remain high

• population grows rapidly



3) Industrial Stage:

• birth rate drops & eventually approaches a balance with death rate

• slowing of population growth

Birth rate

Death rate

Total pop.



4) Postindustrial Stage:

• birth rate & death rates approximately balance

• zero population growth

• population stabilizes at a size much higher than the preindustrial size

• if birth rate declines below death rate negative population growth may even be attained

Total pop.

Birth rate

Death rate

Computer Models of Human PopulationComputer Models of Human Population


This computer model projects what might happen if the world's population & economy continue to grow exponentially at 1990 levels.

Computer Models of Human PopulationComputer Models of Human Population


This computer model projects how we can avoid overshoot & collapse to make a fairly smooth transition to a sustainable future by stabilizing fertility at two children per couple.

Case Studies – Population Case Studies – Population Control in IndiaControl in India


• In 1952, India began the first national family planning program

• The program has been disappointing because of poor planning, low status of women, extreme poverty, & lack of funds

• Couples still have an average of 3.5 children because of the belief that they need children to work & care for them in old age

India

Case Studies – Population Case Studies – Population Control in ChinaControl in China


• Since 1970, China has initiated efforts to better feed its people & control population growth

• Strict population control measures prevent couples from having more than one child

• Although considered coercive, the policy is significantly slowing population growth

China

Case Studies – Immigration in Case Studies – Immigration in the U.S.the U.S.


• As fertility decreases, immigration has become a major source of population increase in the U.S.

• In 1998, the U.S. received about 935,000 legal immigrants & 400,00 illegal immigrants

• Increasing levels of legal & illegal immigrants are expected


Immigration in the U.S.A.!

Immigration in the United States

Should the U.S. reduce the number of immigrants allowed into the country?

Is the U.S. (or other wealthy countries) obligated to accept immigrants from very poor countries?

Human Population & SustainabilityHuman Population & Sustainability


How can governments reduce population growth?• improve access to family planning & reproductive health care

• improve heath care for infants, children, & pregnant women

• encourage development of national population policies

• improve equality between men & women

• increase access to education, especially for girls

• increase the involvement of men in child rearing & family planning

• reduce poverty

• reduce & eliminate unsustainable patterns of production & consumption

chapter 11 human population: growth & distribution © brooks/cole publishing company / itp

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