Sex Composition & Age-Sex Pyramid

• Sex composition is the balance of males and females in a population. It is expressed as the sex ratio.
• Along with age, it is the most basic of the demographic attributes. It shapes marriage, fertility, labour supply and migration, and it reflects the status of women in a society.
• The age–sex pyramid shows age and sex together in one graph. It records a population’s past births, deaths and migration and hints at its future growth.

Sex Composition

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Measurement of Sex Ratio

• The idea is the same everywhere, but the way of expressing it differs:
  • India (Census): females per 1000 males.
    • Sex ratio = (female population ÷ male population) × 1000.
  • United Nations and most countries: males per 100 females. This is also called the masculinity ratio.
  • Some countries (Russia, for example) report the percentage of males or females in the total population. A balanced population is 50 : 50.
• Readers must check the convention before comparing figures.
  • India’s 943 females per 1000 males (2011) is the same balance as about 106 males per 100 females.
• The calculation needs a reliable count of each sex. Under-enumeration of women, common in poor and patriarchal societies, lowers the measured ratio.

Types of Sex Ratio

• Primary sex ratio: the ratio at conception.
  • It cannot be observed directly.
  • The older view held that far more males are conceived. Recent large-sample evidence (Steven Orzack and colleagues, 2015) suggests the ratio at conception is close to 1:1.
• Secondary sex ratio: the ratio at birth, also called the sex ratio at birth (SRB).
  • The natural level is about 104–106 boys per 100 girls, or roughly 943–962 girls per 1000 boys.
• Tertiary sex ratio: the ratio at the time of enumeration, as a census counts it.
  • Unless stated otherwise, “sex ratio” means the tertiary ratio.

Determinants

• The sex ratio at birth.
  • The small natural surplus of boys arises during pregnancy: female embryos are lost more often early in pregnancy, male foetuses more often later. On balance, more boys are born.
  • Sex-selective abortion pushes the SRB well above the natural level where son preference is strong. This happened in China, India, South Korea, Vietnam and the Caucasus (Armenia, Azerbaijan).
• Differential mortality.
  • Males die faster at almost every age: through biology, risky work, accidents, violence, smoking and alcohol.
  • The male surplus at birth therefore shrinks with age. Most populations have more women than men at older ages.
  • Where women’s status is low, the pattern reverses. Neglect of girls, excess female child mortality and maternal deaths remove women faster than men.
• Sex-selective migration.
  • Labour migration is usually male-selective. Areas of in-migration (cities, mines, plantations, the Gulf) gain men; areas of out-migration keep women.
  • Marriage migration of women within India and the migration of women into domestic and care work (Hong Kong, the Gulf, Europe) work in the other direction.
• Wars and conflict kill mostly men. The female surplus they leave lasts for decades.
• Enumeration errors: under-counting of women and girls.

Significance

• The sex ratio decides the marriage market and the size of the labour force.
  • A shortage of women produces “marriage squeezes” and bride trafficking.
  • China’s surplus of young men is one example. In India, women are “brought” into Haryana from Assam, West Bengal and Odisha.
• It is an indicator of women’s status. A deficit of girls signals discrimination before birth and in childhood.
• It shapes fertility and the demand for services, for example health care for elderly widows in ageing societies.

World Pattern

• In 2024 there were about 989 females per 1000 males in the world. Put the other way, this is about 101 males per 100 females (UN World Population Prospects 2024).
  • The world has a slight male surplus because Asia’s two giants (China, India) are male-heavy.
• Male-surplus regions:
  • Gulf states, through male labour migration:
    • Qatar has the lowest ratio in the world: about 403 females per 1000 males, or 248 males per 100 females.
    • It is followed by the UAE (565), Oman (607), Bahrain (612), Maldives (615), Kuwait (636) and Saudi Arabia (652).
  • South and East Asia (China 963, India 939, Pakistan), through son preference, high female child mortality in the past, and sex-selective abortion.
• Female-surplus regions:
  • Former Soviet states: Latvia (1157), Russia (1155), Ukraine (1151), Moldova, Armenia.
    • These reflect very high male mortality, from alcohol, cardiovascular disease, accidents and violence, and the losses of war.
  • Ageing developed countries, where women outlive men by 4–6 years: Japan (1050) and much of Western and Southern Europe.
  • Hong Kong (1220) has the highest ratio in the world, because of female foreign domestic workers from the Philippines and Indonesia and cross-border marriages with women from mainland China.
• Near balance: most of Sub-Saharan Africa and Latin America.
  • Their young age structures mean that the surplus of boys at birth is not yet offset by male deaths at older ages.
• Trend:
  • The global ratio fell slightly as China’s and India’s SRBs rose from the 1980s.
  • It is projected to approach balance by 2100, as SRBs normalise and populations age.
  • South Korea shows that the trend can reverse. Its SRB of about 116 boys per 100 girls in 1990 returned to the natural level by the late 2000s.

Sex Ratio in India

Trend

• India has had a persistent deficit of females since the first census.
• Over the 20th century the ratio declined:
  • 972 in 1901, 946 in 1951 and 941 in 1961.
  • The lowest point was 927 in 1991.
• It then recovered: 933 in 2001 and 943 in 2011, the best since 1971.
• The child sex ratio (0–6 years) moved the other way. It fell for five decades:
  • from 976 in 1961 to 945 in 1991, 927 in 2001 and 918 in 2011.
  • This is the clearest sign of sex selection before birth.
• Sex ratio at birth (Sample Registration System):
  • It improved from 898 in 2014–16 to 918 in 2022–24 (SRS 2024).
  • It was highest in Chhattisgarh (978) and Kerala (974), and lowest in Uttarakhand (872).
• NFHS-5 (2019–21) recorded 1020 females per 1000 males in surveyed households, the first female-majority figure.
  • This is a household survey of the usually resident population. It is not comparable with the census, because it misses men living away for work and those in institutions.
  • Its sex ratio at birth for the previous five years was 929.
  • The NFHS-6 (2023–24) fact sheets, released in May 2026, do not report sex ratios, so NFHS-5 remains the latest survey value.
• The next census, delayed from 2021, will give the first post-2011 count. Its houselisting phase ran in 2026, and population enumeration has a reference date of 1 March 2027.

Spatial Pattern (Census 2011)

• Highest: Kerala (1084) and Puducherry (1037).
  • These are the only two States/UTs with more females than males.
• Lowest: Daman and Diu (618), Dadra and Nagar Haveli (774) and Chandigarh (818).
  • All three are industrial or urban UTs that attract male migrant labour.
• Near balance (970–1000):
  • Tamil Nadu (996), undivided Andhra Pradesh (993), Chhattisgarh (991), Meghalaya (989), Manipur (985), Odisha (979), Mizoram (976), Goa and Karnataka (973), Himachal Pradesh (972).
• Severe deficit: Haryana (879), Delhi (868), Jammu and Kashmir (889), Sikkim (890), Punjab (895) and Uttar Pradesh (912).
• Regional pattern:
  • The south, the north-east and the tribal belt of central and eastern India have favourable ratios.
  • The north-west and the Ganga plain have the poorest ratios.

Rural–Urban Differential

• Rural (949) is higher than urban (929), because men migrate to towns alone and women and children stay in villages.
• The gap is narrowing. The urban ratio rose from 860 in 1951 to 929 in 2011, as more migrants move with their families.
• Rural ratios range from 690 (Chandigarh) to 1078 (Kerala).
  • Five States/UTs have rural ratios of 1000 or more: Kerala, Puducherry, Goa, Chhattisgarh and Uttarakhand.
  • Uttarakhand’s figure reflects the out-migration of men from the hills.
• Urban ratios range from 551 (Daman and Diu) to 1091 (Kerala).
  • Urban ratios are favourable in Kerala, Puducherry, Manipur and Meghalaya.
  • They are balanced in Tamil Nadu.

Child Sex Ratio

• 918 in 2011, with a range of:
  • 834 in Haryana (lowest), then Punjab (846) and Jammu and Kashmir (862);
  • 972 in Arunachal Pradesh (highest), then Meghalaya and Mizoram (970).
• The decline spread from the north-west to the east and south between 1991 and 2011. It followed the spread of ultrasound and prosperity combined with small-family norms.

Causes of the Female Deficit

• Son preference, rooted in patrilineal inheritance, dowry, old-age support from sons and the ritual role of sons.
• Sex-selective abortion, which spread from the 1980s with ultrasound. It is most common among prosperous, small-family households: the “squeeze” of wanting fewer children but at least one son.
• Excess female child mortality, from neglect in nutrition and health care.
• Maternal mortality: the maternal mortality ratio was still 87 per lakh live births in 2022–24.
• Male-selective migration, into cities and industrial UTs.
• Under-enumeration of women.

Consequences and Responses

• Consequences:
  • Marriage squeeze and bride trafficking.
  • Violence against women.
  • Distorted labour markets and sex-ratio imbalance in cities.
• Responses:
  • Pre-Conception and Pre-Natal Diagnostic Techniques (PCPNDT) Act (the PNDT Act of 1994, extended in 2003): bans sex determination.
  • Beti Bachao Beti Padhao (2015): launched in Panipat, Haryana, focused first on the worst-CSR districts.
  • Sukanya Samriddhi accounts.
  • Conditional cash transfers.
• Outcome:
  • Haryana’s SRB has improved.
  • Kerala shows the role of female literacy and status. It combines a favourable ratio, low fertility and the longest female life expectancy among the major states.

Age–Sex Pyramid

Construction

• The age–sex pyramid is a pair of back-to-back horizontal bar graphs:
  • Males on the left, females on the right.
  • Age groups (usually five-year) run from youngest at the base to oldest at the top.
• Bars show absolute numbers or, for comparison between countries, the percentage of total population in each age–sex group.
• Its shape depends on the stage of the demographic transition, and on epidemics, wars, famines and migration.
• The age composition of the population and the dependency ratio are read directly from it.

Types of Pyramid

• Expansive (progressive):
  • Broad base, concave sides and a narrow apex.
  • High birth and death rates. Over 40% of the population is under 15.
  • Stages 1–2 of the demographic transition.
  • Niger, Ethiopia, Afghanistan; India before 2000.
• Stationary:
  • Near-vertical sides up to middle age.
  • Low birth and death rates, so the cohorts are roughly equal and growth is slow.
  • USA, France, Australia.
• Constrictive (regressive):
  • Narrow base, wider middle and upper sections.
  • Fertility is below replacement, and older cohorts outnumber the young.
  • Japan, Italy, South Korea, Germany.
• India today is moving from expansive to stationary.
  • Its base has narrowed since about 2000 as fertility fell to 1.9 (SRS 2024).
  • A bulge in the working ages (15–34) carries the demographic dividend.

The Pyramid as a Record of History

• Every event that changes births, deaths or migration leaves a mark that moves up the pyramid as the cohort ages:
  • Migration:
    • The UAE and Qatar have a huge male bulge at 25–49 from migrant workers, and few old people, since migrants return home.
    • Kerala’s and the Uttarakhand hills’ pyramids show the reverse: a shortage of working-age men.
  • War:
    • Russia still has very few men aged 80+, because of the Second World War and high male mortality.
    • Its 1990s birth slump shows as a notch at ages 25–34.
  • Famine:
    • China’s 1959–61 famine is a notch at ages 64–66 today.
  • Population policy:
    • China’s one-child era (1980–2015) narrowed its base. Its births have nearly halved since 2016.
    • Male surpluses in the young cohorts of China and India record sex selection.
  • Baby booms (USA, Europe, 1946–64) appear as bulges, now near the top. Echo booms follow a generation later.

• Pyramids are also used to project future population:
  • A broad base means population momentum: growth continues for decades even after fertility falls to replacement.
  • A top-heavy pyramid means a rising old-age dependency ratio, shrinking labour forces and pressure on pensions and health care, as in Japan, Italy and South Korea.