Sex Composition

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The proportion of males and females in a population is termed as sex composition.
Its numerical expression is given through the sex ratio.

Measurement of Sex Ratio

Although the concept remains same, methods of calculation vary across countries:
- Russia:
  - Expressed as percentage of male or female population to total population
  - Balanced → 50% male : 50% female
- USA & UK:
  - Number of males per 100 females
- New Zealand:
  - Number of females per 100 males
- India:
  - Number of females per 1000 males
  - Formula:
    - Sex Ratio = (Total female population / Total male population) × 1000
Hence, availability of male and female population data is essential for calculation.

Types of Sex Ratio

Sex composition can be classified into three types:
- Primary Sex Ratio
  - Ratio of female to male population at conception
- Secondary Sex Ratio
  - Ratio of female to male population at birth
  - Also called natural sex ratio
- Tertiary Sex Ratio
  - Ratio of female to male population at the time of enumeration (census)

Determinants and Variations

Primary Sex Ratio
- Deviates from theoretical equality due to:
  - Abortions (male/female selective)
  - Miscarriages
  - Still-births and live birth variations
Secondary Sex Ratio (Natural Sex Ratio)
- Generally shows male dominance at birth
  - Range: 105–107 males per 100 females
- Reasons:
  - Higher male births globally
  - Higher mortality among male babies at birth due to pregnancy-related complications
- Also influenced by:
  - Age-specific mortality differences
Tertiary Sex Ratio
- Determined by:
  - Sex ratio at birth
  - Sex ratio at death
  - Sex ratio of migrants
- Migration plays a crucial role:
  - Economic migration is male-selective
  - Areas of in-migration → excess males
- This pattern is:
  - More prominent in large urban areas and cities
  - Associated with rural–urban migration

World Pattern

The sex ratio (number of females per thousand males) shows significant variation across countries.
Unless specified, sex ratio generally refers to the tertiary sex ratio (measured at the time of enumeration).
At the global level (2021 estimate):
- Females constitute 49.58% of total population
- Global sex ratio: 983 females per 1000 males
Trend of Sex Ratio (World)
- The global sex ratio has shown slight fluctuations over time:
  - Declined from 993 (1980) to 983 (2015)
  - Projected to increase to:
    - 991 by 2050
    - 997 by 2100
Developed vs Developing Countries
- Higher sex ratio (female dominance) observed in:
  - Developed regions → Europe, North America
- Lower sex ratio (male dominance) observed in:
  - Less developed regions → Asia, South America
Country-Level Variations
- Sex ratio varies widely across countries:
  - Lowest: Qatar (~334)
  - Highest: Hong Kong (~1184)
- Very low sex ratio observed in:
  - Gulf and Muslim-dominated countries such as
    - Qatar, UAE, Oman, Bahrain, Kuwait, Saudi Arabia, Maldives
  - Reasons:
    - Male-selective migration
    - Relatively lower status of females
- Globally:
  - Around 66 countries have sex ratio below 1000
  - Around 135 countries/territories have sex ratio above 1000
Sex Ratio in Top 10 Populous Countries (2021)
- Highest:
  - Russia → 1157
  - Mexico → 1041
- Moderate / Near Balance:
  - USA → 1021
  - Brazil → 1037
- Low Sex Ratio:
  - China → 950
  - India → 925 (lowest among top 10)
  - Pakistan → 943
- World Average: 983

Key Observations

Regional Pattern:
- High sex ratio → Europe, North & South America
- Low sex ratio → Asia and Africa
Major Causes of Low Sex Ratio:
- Higher male births
- Female child mortality
- Male-selective migration (especially in Gulf countries)

Spatial Pattern in India

India is characterised by a marked paucity of females in the population.
Trend of sex ratio (females per 1000 males):
- 1901 → 972
- 1991 → 927
- 2011 → 943 (after slight improvement)
The deficit of females is mainly associated with:
- Excess of male births
- High female child mortality
- High maternal mortality
- Low status of women
Factors of Spatial Variation
- Significant inter-state variation exists due to:
  - Male-selective migration
  - Rural–urban differences
  - Socio-economic variations
  - Ethno-religious and caste-based factors
  - Locational characteristics
Rural–Urban Differential
- Due to male-selective rural–urban migration:
  - Urban sex ratio (2011) → 929
  - Rural sex ratio (2011) → 949
- Thus, urban areas show lower sex ratio than rural areas.
State-Level Variation
- Sex ratio varies widely across states/UTs (2011):
  - Highest:
    - Kerala → 1084
    - Puducherry → 1038
  - Lowest:
    - Daman & Diu → 618
    - Dadra & Nagar Haveli → 775
- Only Kerala and Puducherry show female-favourable sex ratio (>1000).
- Near balanced sex ratio observed in:
  - Tamil Nadu
  - Andhra Pradesh
  - Chhattisgarh
Rural Pattern
- Generally higher sex ratio in rural areas
- Range:
  - Lowest → 690 (Chandigarh)
  - Highest → 1078 (Kerala)
- Sex ratio ≥1000 in seven states/UTs
Urban Pattern
- More distorted pattern compared to rural areas
- Range:
  - Lowest → 551 (Daman & Diu)
  - Highest → 1091 (Kerala)
- Female-favourable urban sex ratio in:
  - Kerala
  - Puducherry
  - Manipur
  - Meghalaya
- Near balance in:
  - Tamil Nadu
  - Mizoram
Regional Pattern
- Better sex ratio observed in:
  - Southern India
  - North-Eastern India
- Poor sex ratio observed in:
  - Northern and North-Western states
Child Sex Ratio (0–6 Age Group)
- India (2011): 919 → highly discouraging
- Range across states:
  - Lowest: Haryana → 834
  - Highest: Arunachal Pradesh → 972
- Causes:
  - Excess male births
  - High female child mortality
  - Female foeticide / sex-selective abortion

Age-Sex Pyramid

The shape of age-sex pyramid varies from country to country depending upon:
- Stage of demographic transition
- Incidence of epidemics, wars and migration
Countries with:
- High birth rate and high death rate → Broad base and sharply narrowing top (triangular shape)
- Advanced stages of demographic transition (Stage III/IV) → Narrow base with relatively wider middle and gradual tapering
Thus, the shape of pyramid reflects:
- Stage of demographic transition
- Nature of age structure
- Fertility and mortality patterns

India: Expansive (Youthful) Population

India shows expansive pyramid due to:
- High fertility
- Low life expectancy
Characteristics:
- Broad base → High proportion of children
- Narrow apex → Low proportion of aged population
Indicates:
- Youthful population
- High population growth potential

Ethiopia and Bangladesh: Similar Expansive Pattern

Both countries exhibit expansive age-sex pyramids
Features:
- Wide base → High fertility
- Narrow top → Low life expectancy
Reflect:
- Developing economy
- Early stage of demographic transition

USA and Australia: Constrictive Pyramid

These countries show constrictive pyramids due to:
- Low fertility
- Increasing life expectancy
Characteristics:
- Narrow base → Low birth rate
- Wider middle age groups
- Gradual tapering
Indicates:
- Ageing population
- Advanced stage of demographic transition

Japan: Stationary / Ageing Population

Japan represents stationary and ageing population
Features:
- Very narrow base → Very low fertility
- Wide middle and top → High life expectancy
Situation:
- Fertility sometimes lower than mortality
- Completed all stages of demographic transition