Population, Economy and Society Age and Sex Structure.

Population, Economy and Society

Age and Sex Structure


The age and sex structure of a population has many important implications for that population!

For example this structure: Is the basic determinant of the nation’s labor supply Influences requirements for basic goods and services Influences school attendance Influences economic activity And most fundamentally, it influences a society’s basic

reproductive capacity


Now recall our discussion of the basic measures of demographic processes!

The CBR and the CDR are highly sensitive to the age/sex composition of a population!

The age/sex structure or composition of a population at any time is the result of past trends in: Fertility Mortality Migration


In turn, it influences the current levels of crude vital rates and the rate of population growth since births, deaths and migration occur with unequal frequency at different ages!

OK…We want to explore the following: The current age and sex patterns in different regions of the

world The factors determining age and sex structure The effects of age and sex structures on the demographic

processes Some of the social and economic implications of a population’s

age and sex structure


Sex Structure Age/sex structure is usually described as a series of

“sex ratios”. Most commonly this is the “masculinity” ratio as it

is computed as the number of males per 100 females.

The sex ration at birth in the US is ~105/100 or 105 male births per 100 female births.

Why are more males born?


Since ASMR’s are generally higher for males at every age these ratios tend to gradually decline with age and then fall below the 100 level!

The age at which this happens varies. Beyond this age the number of females begins to

exceed the number of males! This can be quite exaggerated at the advanced ages! We will see later that this associated with a process

called the “feminization of old age”

Age and Sex StructureSex Ratios Circa 2000

Area <15 15 to 64 65+ TotalWorld Total 103.5 98.9 74.8 99.2MDC's 103.2 92.8 65.6 93LDC's 104.3 102.3 87.8 102Africa 100.3 99.6 82.6 99.4E. Asia 102.8 100.2 80.9 100S. Asia 104.6 104.8 85.7 104Europe 104.8 95.3 66.6 94.1L. America 103 99.4 89.2 101N. America 103.8 97.6 78.4 97.5Oceania 105.3 105.5 74.6 103

Age and Sex StructureSex Ratios by Age U.S.

2000

Age US 2000All Ages 94.8<5 104.75 to 9 104.610 to 14 104.415 to 19 103.720 to 24 101.625 to 29 99.830 to 34 98.435 to 39 97.240 to 44 96.145 to 49 94.650 to 54 92.355 to 59 89.460 to 64 86.265 to 69 8070 to 74 72.375 to 79 68.780 to 84 53.285+ 43.7


Age Structure Although chronological age is an unambiguous

concept, census reports on age are subject to a number of errors: Deliberate misstatement “Preferred digits” Exaggeration of age at older ages Carelessness in reporting Ignorance of correct age

Age and Sex StructureU.S.2000

Male 133,551,363 % Female 140,091,910 %

under 5 years 9,791,115 0.073 7.3 under 5 years 9,346,859 0.067 6.75 to 9 years 10,504,352 0.079 7.9 5 to 9 years 10,010,859 0.071 7.110 to 14 years 10,469,540 0.078 7.8 10 to 14 years 9,980,260 0.071 7.115 to 19 years 9,623,303 0.072 7.2 15 to 19 years 9,139,940 0.065 6.520 to 24 years 8,690,853 0.065 6.5 20 to 24 years 8,728,437 0.062 6.225 to 29 years 9,363,065 0.07 7.0 25 to 29 years 9,500,542 0.068 6.830 to 34 years 9,925,396 0.074 7.4 30 to 34 years 10,109,995 0.072 7.235 to 39 years 10,915,338 0.082 8.2 35 to 39 years 11,300,990 0.081 8.140 to 44 years 10,799,229 0.081 8.1 40 to 44 years 11,236,407 0.08 8.045 to 49 years 9,665,666 0.072 7.2 45 to 49 years 10,142,567 0.072 7.250 to 54 years 8,461,727 0.063 6.3 50 to 54 years 8,925,567 0.064 6.455 to 59 years 6,414,817 0.048 4.8 55 to 59 years 6,913,082 0.049 4.960 to 64 years 5,064,864 0.038 3.8 60 to 64 years 5,620,371 0.04 4.065 to 69 years 4,331,961 0.032 3.2 65 to 69 years 5,067,797 0.036 3.670 to 74 years 3,820,807 0.029 2.9 70 to 74 years 4,843,823 0.035 3.575 to 79 years 2,940,284 0.022 2.2 75 to 79 years 4,170,049 0.03 3.080 to 84 years 1,719,227 0.013 1.3 80 to 84 years 2,799,392 0.02 2.085 years and over 1,049,819 0.008 0.8 85 years and over 2,254,973 0.016 1.6

The Dependency Ratio

Pop 0-14 + Pop 65+

DR = ------------------------------- X 100

Pop 15-64

Dependency RatiosCirca 2000

World73.5 L. America 85.7 MDC’s 58.8 N. America 67.2 LDC’s 81.3 Europe 55.9 Africa86.2 Oceania 66.9 E. Asia 69.4 S. Asia 85.0

Percent below age 15 and Over 65

MDC’s = 19% 15% LDC’s = 34% 5% Mid Africa = 47% 3% South Asia = 37% 5% L. America = 33% 6% Europe = 18% 15% N. America = 21% 13%

Median AgeUS 1870-2050

Year Male Female1870 20.2 20.11880 21.2 20.71890 22.3 21.61900 23.3 22.41910 24.6 23.51920 25.8 24.71930 26.7 26.21940 29.1 291950 29.9 30.51960 28.7 30.31970 26.8 29.31980 28.8 31.31990 31.8 34.32000 34.9 37.72025 38.3 41.82050 39.4 43.7

Reading a Population Pyramid

Sex

Age/Year of Birth Populatio

n Size

Cohort/generation

Historical events

Trends

Tracking the Baby

Boom Generation

Click the button below to see

changes in the US population from

1950 - 2050:


Factors determining age/sex structure Migration

Young males are most likely to migrate Impact on the US

In the long term In the short term In small geographic areas

Internationally?Labor surplus and deficit countries!


Mortality Mortality varies with age thus the pyramidal shape of the

population pyramid Higher rates for males affect it Circumstances such as war can also affect it In general changes in mortality don’t affect the age/sex

structure as much as migration or changes in fertility! Fertility

Of critical importance to the age/sex structure Short term changes Long term changes

Changes in fertility and mortality and age/sex structure

Age-Sex Structure of Botswana - 2020


The effects of age and sex structures on the demographic processes!

There is a sort of “feedback” effect here! Captured in the notion of “Population Momentum” The population processes determine the age/sex

structure of a population and that age/sex structure drives the population processes!

The “Rectangularization” of the pyramid!

The “Feedback” effect and “Rectagularization”


Consequences of changes in the age and sex structure!

Education In the MDC’s In the LDC’s

The Economy In the MDC’s In the LDC’s


Politics and Political Behavior In the MDC’s In the LDC’s

Crime Marriage Markets

Stable and Stationary Populations

A Stable population The age structure remains unchanged Fertility and mortality rates have remained unchanged

for some time There is no migration Can be growth

A Stationary population Is stable Has achieved ZPG

Population Projections

“It is easy to predict everything except the future” (Nathan Keyfitz) (Taken from an old Chinese proverb)

Cautions about population projections! It can be very difficult to forecast with accuracy The longer the time period the greater the risk Changes in fertility are generally the most problematic Especially difficult in the LDC’s because of the lack of

data

Population Projections

OK…So what are the current projections? We often rely on the UN’s Population Division for

our projections! (Our Census Bureau also does them)

They usually take the form of three “scenarios” which are based on assumptions about fertility and mortality (Remember that we said that fertility is the most critical element and remember that if we are talking about the world we don’t have to worry about migration but if we are talking about the US we do!)

Some Population Projections for the U.S.

YearMiddleSeries

Lowest Series

HighestSeries

ZeroIntnl.MigrationSeries

2005 287,716 284,000 292,339 280,8592010 299,862 291,413 310,910 287,7102015 312,268 297,977 331,636 294,7412020 324,927 303,664 354,642 301,6362025 337,815 308,229 380,397 307,9232030 351,070 311,656 409,604 313,2192035 364,319 313,819 441,618 317,5342040 377,350 314,673 475,949 321,1672045 390,398 314,484 512,904 324,4492050 403,687 313,546 552,757 327,641

Some population Projections for the World

Projections for the world: Low 7.3 billion Medium 8.9 billion High 10.7 billion

The world is currently growing at ~1.3% per year or a doubling time of 53 years!

Zero Population GrowthZPG

What are the consequences of achieving it now versus later? Social? Political? Economic?

Either way there will be shifts in the age/sex structure that will necessitate adjustments in society!

ZPG in the world?

Population, Economy and Society Age and Sex Structure.

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