Population Age Structure
*** What Are Age Structure Diagrams? ***
Even if the replacement-level fertility rate of 2.1 were magically achieved globally tomorrow, the world
population would keep growing for at least another 50 years.
The reason for this is a population's age structure: the proportion of the population (or of each sex) at each
age level.
Population Geographers typically construct a population age structure diagram by plotting the percentages
of numbers of males and females in the total population in each of three age categories:
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prereproductive (ages 0-14)
reproductive (ages 15-44)
postreproductive (ages 45 and up)
Generalized population age structure diagrams for countries with:
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rapid (1.5-3%) growth rates/slow (0.3-1.4%) growth rates
zero (0-0.2%) growth rates/negative growth rates
*** How Does Age Structure Affect Population Growth? ***
Any country with many people below 15 years old (represented by a wide based population structure
diagram) has a powerful built-in momentum to increase its population size unless death rates rise sharply.
The number of births rises even if women have only one or two children because of the large number of
girls who will be soon moving into their reproductive years.
In 2002, 30% of the world's people were under 15 years old.
These 1.9 billion people are poised to move into their reproductive years
This powerful force for continued population growth, mostly in developing countries, could be slowed by:
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an effective program to reduce birth rates
a sharp rise in death rates
Suppose that somehow the world's average TFR fell immediately the replacement level, 2.1 children.
Even then more than 75% of the world's projected population growth would still occur.
We live in a demographically divided world. The population structure diagrams of developed and
developing countries are very different.
Comparing population data for the US, Brazil and Nigeria further illustrate the differences.
Population size has stabilized or is declining in Japan and most European countries.
However, population size is expected to double or even triple before stabilizing for many developing
countries with fairly large populations and large numbers of people under age 15.
Example countries are:
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Nigeria
Ethiopia
Mexico
Brazil
Bangladesh
Pakistan
For example, 44% of Nigeria's population is under the age of 15 and its TFR is 5.8 children per woman.
As a result, Nigeria's current population of about 130 million is projected to reach about 305 million by
2050.
*** How Can Age Structure Diagrams Be Used To Make Population and Economic Projections? ***
The 79 million person increase that occurred in the US population between 1946 and 1964, known as the
baby boom, will continue to move up through the country's age structure as the members of this group grow
older.
Tracking the baby boom generation in the US (1, 2).
Baby boomers now make up nearly half of all adult Americans.
As a result, they:
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dominate the population's demand for goods and services
play an increasingly important role in deciding who gets elected and what laws are passed.
Baby boomers who created the youth market in their teens and 20s are:
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now creating the 50-something market
will soon move on to create the 60-something market
Many Americans are unaware that Social Security taxes on workers in the current generation are used to pay
current beneficiaries.
Number of workers supporting each beneficiary of the Social Security program in the US, 1945-2075
(projected).
As the number of workers supporting each beneficiary declines, it will be necessary to:
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dramatically increase the Social security taxes on workers
decrease retirement benefits
extend the official retirement age
make up the shortfall from other government funds (which could greatly increase income
taxes).
Much of the economic burden of helping support a large number of retired baby boomers will fall on the
baby bust generation (also called generation X): the 44 million people born between 1965 and 1976
(when TFRs fell sharply and have remained below 2.1 since 1970)
Retired baby boomers are likely to use their political clout to force the smaller number of people in the baby
bust generation to pay higher income, health-care and Social Security taxes.
This could cause resentment and conflicts between the two generations.
In some respects, the baby bust generation should have an easier time than the baby boom generation.
Fewer people will be competing for
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educational opportunities
jobs and services
Labor shortages may drive up their wages, at least for jobs requiring education and technical training
beyond high school.
But members of the baby bust group may find it difficult to get job promotions as they reach middle age
because members of the much larger baby boom group will occupy most upper-level positions.
Many baby boomers may delay retirement because of
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improved health
the need to accumulate adequate retirement funds
extension of the retirement age needed to begin collecting Social security
The baby bust generation is being followed by the echo-boom generation consisting of about 83 million
people born between 1977 and 2000.
This largest generation ever, also know as generation Y, will soon have more economic power than their
baby boom parents.
Population age structure booms and busts create social and economic changes that ripple through a
society for decades.
*** What Are Some Effects of Population Decline from Reduced Fertility? ***
Population geographers and health officials project that the current HIV/AIDS epidemic will claim more
lives (mostly in Africa and eventually in India and China) in the early part of this century than WWII did.
The HIV/AIDS epidemic ravaging Africa kills more than 6000 people each day.
This number of deaths is expected to double in the next 10 years.
Hunger and malnutrition kill most infants and children, but AIDS kill many young adults.
This change in the young adult age structure of a country has a number of harmful effects:
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a sharp drop in life expectancy. In African countries, where 10-35% of the adult population
is infected with HIV, life expectancy could drop to 35-40 years.
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a loss of a country's most productive young adult workers and trained personnel. This
greatly increases the dependency ratio -- the number of productive adults available to support the young
and elderly.
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a sharp rise in the number of orphans whose parents have died from AIDS. In Africa, the
AIDS epidemic could easily result in 40 million orphans by 2010.
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a drop in food production because of a decline n the number of adults producing food.
Analysts call for the international community, especially developed countries, to develop a plan to help
affected countries to
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reduce the spread of HIV through a combination of improved education, health care and
family planning.
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restore economic progress through
debt relief
incentives to encourage investment
financial assistance for education and health care
sending in volunteer teachers and health care and social workers to help compensate
for the missing young adult generation