Population ageing is the shift in a population's age composition towards older ages. It is measured as a change in structure, not in individual lifespans: a population ages when the proportion aged 60 and above rises, even if nobody lives longer than before. Two forces produce it. The first and stronger is fertility decline, which narrows the base of the age pyramid so that each successive cohort entering life is smaller than the last. The second is rising longevity, the result of falling mortality at older ages, which thickens the apex. Ageing is therefore the predictable late stage of the demographic transition rather than an anomaly.

The distinction between the two drivers matters analytically. Ageing driven by fertility decline is a change in the relative size of cohorts and is largely irreversible once fertility has been low for a generation; ageing driven by longevity is an achievement of public health. Confusing them produces the common error of treating ageing as a crisis of survival rather than a consequence of smaller families.

Measuring an ageing population

Three measures recur. The share of persons aged 60 and above — India's conventional cut-off, against 65 in most Western statistics — is the simplest. The old-age dependency ratio expresses persons aged 60 and above per hundred in the working ages of 15 to 59; it is a crude device, since it counts by age rather than by actual economic activity, and in India large numbers of older persons continue working while many younger adults are outside paid employment. Median age captures the whole distribution in one number and is the best summary of how young or old a population is. Analysts also distinguish the young old from the oldest old, because needs for care and health spending rise very steeply after about eighty.

Two related concepts organise the policy discussion. The demographic dividend is the temporary period when fertility has fallen but the large cohorts born earlier are in the working ages, so the dependency burden is unusually light and savings and output can rise — a possibility, not an automatic gain, since it is realised only if those cohorts are educated, healthy and employed. The ageing window is the interval before the dividend closes, during which a country must build the pension, health and care institutions that its older population will need. Countries that grew rich before growing old had decades; India's window is comparatively narrow.

The feminisation of ageing

Older populations are disproportionately female, because women outlive men almost everywhere. This produces a distinct set of disadvantages that sociologists group under the feminisation of ageing. Wives are typically younger than husbands and survive them, so old age for women is heavily an experience of widowhood, while most older men die married and cared for by a wife. Widows face weaker practical claims on property despite formal legal equality, and in many communities restrictions on dress, diet, remarriage and ritual participation. Their lifetime work has more often been unpaid or informal, so they rarely hold contributory pension entitlements and depend on non-contributory assistance or on sons. Living longer with more years of disability and less income is the characteristic outcome: women's greater longevity translates into more years of dependency, not more years of security.

India's internal contrast

India is ageing unevenly, and the unevenness follows the map of fertility decline. Kerala and Tamil Nadu, which reached replacement-level fertility earliest, already have age structures resembling those of much richer societies, with high proportions of older persons, a high median age and substantial old-age institutional demand. Several northern states — Bihar, Uttar Pradesh, Madhya Pradesh, Rajasthan — remain comparatively young, with fertility having fallen later and a large cohort still entering the labour force. Census of India age distributions and Sample Registration System data document the divergence consistently, and the Longitudinal Ageing Study in India has extended it to health and living arrangements. The policy implication is that India is simultaneously a dividend economy and an ageing one, and that a single national programme fits neither: the southern states need care and pensions now, the northern states need schools and jobs.

Interstate migration sharpens the contrast. Young workers move from the younger states towards the older and richer ones, ageing the sending regions faster and leaving older parents behind. Kerala's long history of Gulf migration has produced a recognisable household form in which older persons live alone or as a couple, supported by remittances but not by co-residence.

Care, pensions and the family

The classical Indian answer to old-age security was the joint family — co-residence, filial obligation and the transfer of authority alongside property. That arrangement is weakening under migration, smaller sibling sets, women's employment and urban housing. The intergenerational contract also assumed the availability of a daughter-in-law's unpaid labour; where she is employed, the labour has to be bought or forgone. Meanwhile formal provision remains thin: contributory pensions cover mainly organised-sector and government employment, leaving most older Indians who worked informally reliant on modest social-assistance pensions, family transfers or continued work. Legislation obliging children to maintain elderly parents, and programmes for geriatric health care, acknowledge the gap without closing it. The substantive questions are therefore about care — who provides it, at what cost to women's employment, and whether it is to be socialised — about health financing for chronic non-communicable disease, and about income security for those with no contributory record.

For the UPSC answer

Begin by separating the two causes — fertility decline narrowing the base and longevity thickening the apex — because most weak answers treat ageing as merely people living longer. Use the three measures precisely, and note the limits of the old-age dependency ratio in a country of extensive informal work. Give the Kerala and Tamil Nadu versus northern-states contrast as the central Indian illustration, and use it to argue that India must reap a dividend and prepare for ageing at the same time. Close on the feminisation of ageing and on the mismatch between a declining joint-family support system and limited pension coverage — that is where the sociology, rather than the demography, of ageing lies.

References & further reading

  1. United Nations Department of Economic and Social Affairs. World Population Ageing (report series). United Nations.
  2. Bloom, D. E., Canning, D. and Sevilla, J. (2003). The Demographic Dividend. RAND Corporation.
  3. Rajan, S. I., Mishra, U. S. and Sarma, P. S. (1999). India's Elderly: Burden or Challenge? Sage.
  4. International Institute for Population Sciences (2020). Longitudinal Ageing Study in India, Wave 1. IIPS.
  5. National Statistical Office (2021). Elderly in India. Government of India.
  6. Dyson, T. (2018). A Population History of India. Oxford University Press.