Components of Population Growth: Birth, Death, Migration

The Three Components of Population Change

Sociology Optional Notes {PDF}

Complete Notes Package (Paper I & II) | 1000+ Pages | Instant Download

Discounted Price | Buy Now @ ₹600 →

• Population change in any territory is the net result of only three processes: births (which add to the population), deaths (which subtract from it), and migration (which redistributes it, adding to a destination and subtracting from an origin without changing the world total). The crude birth rate and crude death rate are both conventionally expressed per thousand of the population in a given year, which makes them comparable across regions and time periods regardless of the size of the underlying population.
• The classical account of how these three components interact over the course of a country’s development is the demographic transition model — a society moves from a stage of high birth and death rates (population roughly stable despite high fertility, because mortality is equally high), through a transitional stage where death rates fall faster than birth rates (population grows rapidly), toward a stage where birth rates eventually fall to match the lower death rate (population growth slows and stabilises). India’s own population history, traced in the companion article on population size and growth, is essentially this transition unfolding unevenly across a single vast and regionally diverse country — with some states like Kerala and Tamil Nadu already at the far end of the transition, and others like Bihar still moving through its middle stages.

Why India’s Death Rate Fell Sharply After 1921

• Before 1931, both birth and death rates in India were high, and it was specifically the death rate that began to fall sharply after 1921, while the birth rate fell only slightly — the defining asymmetry of the country’s demographic transition.
• Several factors explain the decline in mortality:
  • Control over famines and epidemic diseases. The major epidemic diseases of the pre-1921 period were fevers, plague, smallpox, and cholera, but by far the largest single mortality event was the influenza epidemic of 1918-19, which killed roughly 12.5 million people, about 5% of India’s population at the time. Diseases like malaria, tuberculosis, diarrhoea, and dysentery continued to cause deaths well after this, though at nowhere near the scale of the historic epidemics — localised outbreaks such as the 1994 Surat plague and the 2006 dengue and chikungunya episodes show that epidemic risk persists even as its overall demographic weight has fallen.
  • Medical and sanitary improvements. Advances in medical treatment, mass vaccination programmes, and sanitation infrastructure directly reduced deaths from communicable disease.
  • Reduced famine mortality. Famines were historically a major, recurring source of excess mortality, driven by chronic poverty and malnutrition in an agro-climatic setting highly vulnerable to rainfall variation, compounded by inadequate transport, communication, and state response. Amartya Sen’s influential intervention here is that famines were not necessarily caused by an actual shortfall in food grain production — they were equally a “failure of entitlements”, the inability of people to buy or otherwise access food that existed but that they could not afford or claim. Improvements in agricultural productivity (especially through irrigation expansion), transport, and state relief measures have since drastically reduced — though not eliminated — deaths from starvation; the National Rural Employment Guarantee Act is a contemporary state response aimed at exactly this residual risk in backward rural regions.

Why India’s Birth Rate Has Fallen More Slowly

• Unlike the death rate, the birth rate has not registered a comparably sharp fall, for reasons that are sociological rather than purely medical or administrative.
  • Birth rate as a socio-cultural phenomenon. Fertility behaviour is embedded in norms around marriage, family size, and gender roles, and such norms change far more slowly than public health infrastructure can be built.
  • Prosperity’s downward pull operates with a lag. Rising prosperity does exert a strong downward pull on birth rates, but this effect strengthens only once infant mortality has already declined and levels of education and awareness have risen — meaning the birth-rate decline structurally lags the death-rate decline by design, not by policy failure.
  • Sharp regional and state variation in fertility. States such as Kerala and Tamil Nadu brought their total fertility rate (TFR) down to around 2.1 and 1.8 respectively by the early 2000s — Tamil Nadu’s figure sitting almost exactly at “replacement level” (the TFR, conventionally 2.1, required for a generation to exactly replace itself), while Kerala’s was already below replacement, implying eventual population decline there in the absence of in-migration. By contrast, Bihar, Madhya Pradesh, Rajasthan, and Uttar Pradesh historically retained TFRs of 4 or higher; these few high-fertility states, accounting for nearly 45% of India’s population as of 2001, were projected to contribute about half of all population growth up to 2026, with Uttar Pradesh alone expected to account for close to a quarter of the national increase.
    • This regional divide persists in the most recent data: per the National Family Health Survey (NFHS-5, 2019-21), India’s overall TFR has fallen to 2.0 — marginally below the replacement level of 2.1, meaning the country has reached replacement-level fertility in aggregate. Nearly every major state now sits below 2.1, with the sharp exception of Bihar (TFR 3.0) and Meghalaya (2.9), while urban TFR nationally (1.6) sits well below rural TFR (2.1), so the north-south and rural-urban fertility divides identified by these older figures remain very much intact even after two more decades of overall decline.
• The specific socio-cultural causes of a high birth rate, as documented in this literature, include:
  • Customs of early marriage, particularly in rural areas — early-married persons have historically had more children over their reproductive lifetime, which is why the legal minimum marriage age (18 for women, 21 for men) functions as a demographic as much as a welfare intervention.
  • Illiteracy and poverty, operating through two linked mechanisms: less-educated women tend to have more children, and poor households have historically viewed additional children as additional earning hands, even though in practice this rarely improves household welfare and instead perpetuates a cycle of child labour and low education.
  • Preference for a male child, a bias found across both literate and illiterate households, which frequently leads couples to continue having children until a son is born — a dynamic this series returns to directly when discussing the declining child sex ratio.

Migration: Concepts and Definitions

• Migration is defined by demographers with a shared emphasis on relative permanence of the move rather than distance or motive. Everett Lee defines it broadly as “a permanent or semi-permanent change of residence,” placing no restriction on distance or on whether the move was voluntary. Eisenstadt frames migration as “the physical transition of an individual or a group from one society to another,” typically involving abandoning one social setting for a different one. Mangalam similarly stresses the relatively permanent shifting of a “collectivity” — the migrants — from one geographical location to another.
• Migration is classified along several dimensions:
  • Direction relative to national boundaries — immigration and emigration (international) versus in-migration and out-migration (internal).
  • Type of internal movement — rural-to-rural (R-R), rural-to-urban (R-U), urban-to-urban (U-U), and urban-to-rural (U-R), each with a distinct socio-economic profile.
  • Duration and range — long-range versus short-range or seasonal migration, and one-off moves versus chain migration, where migrants from one sub-region cluster into specific destinations and occupations because earlier migrants from the same community have already established a foothold there (documented, for instance, in the concentration of workers from one part of Kumaon in particular Jaipur hotels, and Bihar/eastern Uttar Pradesh labourers in Punjab and Haryana’s agriculture).
• Jan Breman’s observation that caste and religion act as “signposts” for migrants — meaning migrants cluster into specific destinations and occupations along caste and religious lines to secure social and economic support in an unfamiliar setting — captures why migration streams are rarely as anonymous or individualised as pure economic models of labour movement suggest.

Why People Migrate: Push, Pull, and Push-Back

• Migration decisions are conventionally explained through push factors (conditions driving people out of the origin) and pull factors (conditions attracting them to the destination), though this framework needs at least one further refinement to fit the Indian case.
  • Push factors from rural areas include the inability to find sufficient work locally, and the accelerating decline of common property resources — village ponds, forests, and grazing lands — which historically let land-poor households survive without owning land. As these resources are privatised or exhausted, households that once obtained fuel, fodder, and supplementary food for free must now buy these in the market, deepening the very hardship that pushes them toward the city, at the same time as cash-earning opportunities in the village remain limited.
  • Pull factors toward cities include better job opportunities, amenities, and living standards, reinforced by mass media and communication channels that now carry images of urban lifestyles into even remote villages, normalising migration and consumption aspirations that earlier generations did not share.
  • The anonymity of the city functions as a distinct social pull. For socially oppressed groups such as Scheduled Castes and Scheduled Tribes, urban anonymity can offer partial protection from the daily humiliation of caste identification in a village where everyone knows their status. Conversely, it also allows poorer members of socially dominant rural groups to take up low-status urban work they could not perform without loss of face in their home village.
  • Ashish Bose’s “push-back factor.” Not every pull is realised: Bose notes that India’s urban labour force is already large, urban unemployment rates are high, and pools of underemployed urban workers exist, all of which act as deterrents that “push back” against fresh rural-to-urban migration flows — a useful corrective to any account that treats cities as an unlimited absorptive sink for surplus rural labour.
• Migration produces consequences across several registers simultaneously — economic (remittances, labour supply shifts), demographic (age-sex selective movement, since migrants skew young and often male), social (weakened joint-family ties, altered caste dynamics at both ends), and psychological (the strain of relocation and, at times, the loneliness explored in the “Emerging Issues” article’s discussion of elderly parents left behind in villages).
• Comparatively, China manages internal migration through its hukou household-registration system, which historically restricted rural residents’ formal access to urban services even after they physically relocated — a far more state-controlled approach than India’s largely unregulated, market-driven internal migration.

The Scale and Direction of India’s Migration and Urbanisation

• As of the 2011 Census, roughly 69% of India’s population still lived in villages, with the urban share continuing its steady climb from about 11% at the start of the twentieth century. This is not simply a matter of raw numbers: processes of modern development mean the economic and social weight of the agrarian-rural way of life declines relative to the industrial-urban way of life even where most people still physically live in rural areas — agriculture’s share of GDP has fallen continuously even as it continues to employ a much larger share of the workforce than its GDP contribution would suggest.
• Migration is overwhelmingly concentrated in the biggest cities rather than spread evenly across the urban system: India has over 5,000 towns and cities, yet more than two-thirds of the urban population lives in a much smaller set of million-plus cities, whose infrastructure struggles to keep pace with the rate of in-migration. This concentration is precisely why India’s public discourse — dominated by media coverage of a few metropolises — can give a misleadingly “urban” picture of a country where rural areas still hold decisive political weight.
• Contemporary scale (2025 estimates): internal migration in India is now estimated to involve more than 600 million people — about 42% of the population — a substantial rise from the roughly 450 million recorded in the 2011 Census, driven by continuing urbanisation, recurring agrarian distress following the pandemic, and structural shifts in the labour market.
  • By type, rural-to-urban migration remains the single largest stream (around 25.2% of all internal migration per NSSO-style estimates), followed by urban-to-urban (22.9%), urban-to-rural (17.5%), and rural-to-rural (4.4%) movement — a composition that shows urban destinations, not rural ones, now dominate India’s internal mobility.
  • Migration remains sharply gendered in its motive: roughly 86.8% of female migrants move for marriage, while close to half of male migrants (49.6%) move in search of employment — meaning the same aggregate migration figures conceal two largely distinct social phenomena depending on the migrant’s sex.
  • Because the delayed 2021/2027 Census has left a significant data gap on internal migration specifically, the Economic Advisory Council to the Prime Minister has proposed tracking migration through non-traditional proxies — railway ticketing data, banking transaction records, and telecom mobility data — until a fresh, comprehensive count becomes available.