At traffic intersections, drivers in Delhi tune out the brown-haired, snot-nosed waifs who tap and scratch insistently at their car windows. Sometimes, the children are joined by equally ragged parents, mostly in their 20s, trying to sell cheap Chinese-made junk – from plastic flowers to cellphone and steering-wheel covers. The defining feature of destitution in North India appears to be youth. These are the people who should – but are unlikely to – fuel India's great demographic dividend: The productivity and energy that should ideally flow from a country where more than half the people are under 25 years of age. Much has been written about that dividend and how India could be on the cusp of letting it lapse, as it fails to adequately educate and keep healthy the million young people who join the job market every month.

Down South in Bengaluru, the scene at traffic signals varies substantially, although it is equally depressing. Almost all the destitute are elderly. The braver ones hesitantly touch windows with lined, calloused hands. Mostly, they stand at a distance, in silence, palms open. Move on from the signals and the widespread distress of senior citizens is apparent. There is the shrunken, old woman who sits outside my grocery store without a word, moving only when a shopper offer alms – almost all the others are old women, outside the church, the mosque, the bakery. For those who tell me this is all part of a racket, my answer is: Even if that were true, how desperate must these people be to subject themselves to such humiliation at this age.

Ageing India

But beyond the remarkable ability of Indians to look away from – or not see – destitution, whether among the young or elderly, lies a story of swiftly changing demographics that could wipe off India's promise as a youthful, energetic nation, the world's fastest-growing economy. Sooner than we realise, India is starting to age, the old people I encounter a disturbing reminder of how unprepared the country is for old age.

“Industrialisation, urbanisation and migration of population have brought the concept of nuclear family, as a result of which a section of the family, primarily the elders, are confronting the problems of financial and physical support," writes TCA Anant, the government's chief statistician, in the foreword of a 2016 Central Statistics Office report on India's ageing. In the 10 years to 2011, the population of Indians 60 and older grew 27 million, a 35% increase over 2001, and the largest increase over a decade, says the report.

The share and size of the elderly population is steadily rising. There are now 104 million elderly Indians. Together, they would constitute the world's 14th largest country; 71% live in rural areas where medical and psychological support is minimal. By 2050, the number of sexagenarians will rise to 300 million, a three-fold jump, predicts a report from CRISIL Research, a research agency.

North, South divide

The future, then, appears to show fewer children and more elderly, but parse the data and the details get complicated.

After years of reasonably good healthcare, rising literacy and infant survival rates, 10 states, including South India's big four, virtually form a country distinct from the giants of the Hindi heartland. India's fertlity rate is now 2.6, the number of children born to each woman, but the rate in the southern states has fallen below two. That is below the replacement level of 2.1, the level at which population neither increases nor decreases. Karnataka, Kerala, Tamil Nadu and Andhra Pradesh (including Telengana) have fertility rates that match the UK, Sweden, the Netherlands and Norway – 1.7 to 1.9 children per woman. Fertility rates in six other states – Punjab, Himachal Pradesh, Maharashtra, West Bengal, Jammu and Kashmir and Delhi – have also fallen below replacement levels.

In contrast, women in the cow-belt states of Rajasthan, Uttar Pradesh, Bihar and Madhya Pradesh are popping out three children or more; Chattisgarh and Jharkhand are just below three. These fertility rates are in line with countries like Haiti, Lesotho and Guatemala. In 2011, 505 million people lived in these six states, whose population surges will take India past China in six years and keep it still young at an average age of 29 by 2020, when China's will be 39, the US', 40.

Bleak fallout

It isn't clear when India's population will stop growing. It could be as late as 2050 (by which time the average Indian will be 37), earlier if rising literacy and female emancipation holds down family size, a bleak prospect in the patriarchal north.

Falling fertility and fewer children implies that three southern states (Kerala, Goa and Tamil Nadu) contain the highest proportion of elderly in India, my colleague Saumya Tewari has written. As family size shrinks and community support fragments, familial ties that offer support to the infirm and elderly are fraying. Those old people on the streets of relatively prosperous Bengaluru, I believe, offer anecdotal evidence of this phenomenon.

A labour shortage is also evident in large swathes of the southern economy. Internal migration tends to compensate and explains why despite below-replacement-level birth rates, populations continue to rise in the south, Maharashtra and West Bengal. Vacant slots are filled by migrants from the North and the Northeast, which has the least proportion of elderly people in India. This filling of vacant slots is visibly evident in the form of migrants from Bihar and Uttar Pradesh into Mumbai and Kolkata. A quieter migration was revealed three years ago in Bengaluru when thousands of northeasterners streamed out of the city in panic after widespread rumours of attacks against them.

The youth bulge of the North and Northeast and the ageing of the South (and some other states) have two implications in the years to come. First, working Indians will have more dependents to look after, young children and old people. Second, India's overall youth bulge can only delay its greying.

Little preparation

The old-age dependency ratio – the proportion of people above 65 who do not work for every 100 people aged 15 to 64 – has risen by four percentage points over half a century to 2011. That may not sound like much, but given India's numbers, this means every family has likely had more elderly people to support, a burden that will soar. Between 2000 and 2050, India's old-age dependency ratio will go from 13% to 33%, said the Central Statistics Office report.

This is especially bad news for women, who are surviving better and growing older in greater numbers than men, without being any more independent or financially secure than before. These developments might also explain why there appear to be more destitute women than men. India had 53 million women above 60 in 2011, compared to 51 million men, a situation that has reversed since 1991, when there were more elderly men than women.

As India ages, social-security spending, which the government is now trying to trim, will increase. Fewer working people means fewer taxpayers and less money available to spend on things that will grow the economy, although medical services will clearly be a high-growth area. Resources will shrink, expenditure will rise and the government, warns the Central Statistics Office, must be prepared for “a double whammy”. It says: “New priorities must be added to the scarce resources for social programs for elderly, while still having to deal with the problems of the younger populations.”

Currently, no one appears prepared for India's greying, not families, not companies, not the government. Horror stories abound in the media of old people turned out, murdered while living alone, cheated out of their life savings by fraudsters and their own children.

In the private sector, no more than 8% of retirees have pensions, while nine in 10 have no health insurance or assured incomes, said the CRISIL report.

Government-funded care for the elderly is limited. Over four years to 2016, the central government provided no more than Rs 34 crore to build and maintain old-age homes, day care centres and mobile medicare units for indigent senior citizens, according to an analysis by researcher Nishtha Bharti for IndiaSpend. But five states, adept at working through Delhi's bureaucracy but with no more than 32% of India’s population of sexagenarians, cornered 71% of that money.

For instance, with a fertility rate of 3.4 children per woman, India's most populous state, Uttar Pradesh, is at the heart of India's youth bulge, but it also has more people above 60 than any other state: 15 million or 14.9% of its population. Yet, UP got 3.2% of central funds for the elderly, Bharti found.

As on the streets, old-age care in India appears to boils down to chance, grit and survival of the fittest.

Samar Halarnkar is editor, IndiaSpend.org, a data-driven, public-interest journalism non-profit. This fortnightly column will track and interpret India's transformation.