This document discusses key concepts related to age and sex structure of populations including: - Age and sex cohorts that are used to analyze population structures such as 0-4, 5-9, etc. and how groups like children, youth, and elderly are defined. - Metrics like sex ratio, dependency ratio, and median age that provide insights into the distribution of populations. - Factors that influence sex ratios and how they typically change with age. Son preference is also discussed. - Dependency ratios measure the economic burden on the working population from youth and elderly dependents.

1. Section 3
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Presentation of data
Sex ratios
Son preference
Dependency ratios
Population aging

2. Age and sex structure
• This is the distribution of the population by age and sex within a given
year.
• The structure of the population is worth studying because different
groups in the population have different needs.
• Different groups are more at risk of experiencing a particular
demographic event. ( females 15-49 the risk of a maternal death)
• Help us to identify and predict changes in the population over time.
Provides us with a quantitative basis for policy analysis and
formulation
• Education, social security,health, employment, housing.
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3. • Age data is collected by single year of age
• But present in 5 year cohorts to make
analysis easier
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0-4
5-9
10-14
15-19

4. Groups in the population
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<1 year infant
0-18 children
10-19 adolescents
15-24 youth
10-24 young people
0-14 dependent young
15-64 working age
65+ or 60+ elderly
60-74Young elderly
75+ Old elderly
80+ disabled elderly

5. Classification of populations
• Populations may be classified based on the
relative proportions in the young and elderly
cohorts
• Young population has 35% of its members under
age 15 years
• Old population has 10% of its members over 65
years.
• Problem may arise when a population exhibits
both characteristics.
• The median age allows for a mutually exclusive
classification.

6. Median age
• The age that divides the population in half.
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Population with a median age
< 20 years is a young population
20-29 is a population of intermediate ages
30+ is an old population

7. Sex ratio
• This is the proportion of males in the population per every
100 females
• Cal:
males
Females
X 100
Barbados 1960
105519 X 100
126811
83.20 males per 100 females
Barbados 1990
118556
X100
128730
92.0 males per 100 females

8. Patterns in sex ratio
• Shows a constant pattern for most countries
• Usually highest at birth, about 102-105 males per 100 females.
• Although more male babies are born than female babies, the
probability of dying at birth (< 1 year) is higher for male children
• This causes the sex ratio to fall steadily with increasing age. The sex
ratio is almost even in the early adult years and decreases further in old
age.
• During old age the ratio is at its lowest as life expectancy is on average
3-5 years higher for females
• Men mature slower and die earlier than women

9. CHANGES IN THE SEX RATIO IN
JA
Age
group
Total
1943
1970
1991
2000
93.7
95.5
96.2
96.9
0-4
100.3
101.6
103.2
103.7
5-14
100.8
101.0
101.3
102.6
15-29
87.8
92.8
95.1
96.0
30-44
97.2
89.1
93.7
92.2
60+
76.2
83.9
84.1
86.5

10. Determinants
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Affected by relative patterns of
Births
Deaths
Migration
However, these patters must show greater
selectivity of a given sex (biased towards M or F)
• Major wars also lower the sex ratio

11. Son preference
• The tendency for parents to prefer male children
over female children
• where son preference is strong, mortality for girls
in the second to fifth year of life after birth is
higher than that of boys
• Where fertility is high couples may continue to
have more children than they want as they attempt
to get a son.
• Where fertility is low selective abortions and
female infanticide is common

12. Manifestations of son preference
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Female infanticide
Female neglect
Boys being better fed
Given earlier medical attention for illness
Other favorable attention

13. Why are male children preferred
over females?
• Old age security
• Needed to perform certain religious rituals
• Status

14. Countries
• In Eastern Asia, son preference is strong and
fertility low.
• In China and Republic of Korea 110 boys per 100
females.
• At least 60 million girls who would otherwise be
expected to live are missing due to selective
abortions or relative neglect
• Laws in India and China ban sex-determination
testing .
• Need to increase the status of women

15. Dependency ratio
• This is a measure of the economic burden
shared by the working age population.
• the ratio gives us the number of persons in
the population who are theoretically
dependent on the working age population
for economic and social support.

16. Population groups
• youth dependents- persons 0-14 yrs
• Old age dependents – persons 65+ yrs
• Working age population – 15-64 yrs

17. Calculation
• Total dependency ratio
Population 0-14 + 65 and over X100
Population 15 – 64
Barbados 1980
78.0 dependents per 100 persons in the
working age group

18. Youth dependency ratio
• Youth dependency ratio
Population 0 -14
X100
Population 15 – 64
Barbados 1980
52.6 youth dependents per 100 persons in the
working age group

19. Aged dependency ratio
• Aged dependency ratio
Population 65 and over
Population 15 – 64
X100
Barbados 1980
25.4 dependents per 100 persons in the
working age group

20. Problems
• Not all persons in the dependent age group
are dependent
• Some children are working
• Elderly may still be employed or live on
their savings.
• Some persons in the working age group are
not working

21. Advantages
• Gives a rough estimate of the economic burden
shared by the working age pop
• compare changes in populations over time
• Gives us an indication of how rapidly the
population is aging
• Young populations will have a high dependency
ratio
• A ratio of 1 means that the working age
population is carrying a heavy load. Especially