On the cusp of a staggering rise in the number of old people, the developed world appears in the early stage of a “greyquake”, “silver time bomb”, or “grey tsunami”. The number of centenarians in most countries has more than doubled every decade over the last fifty years. Hallmark Cards informs that it now sells some 100,000 100th birthday cards annually.

Britain alone now has some 15,000 centenarians against just 24 in 1917. The share of the over-65 population in rich countries is projected to rise to 27 per cent by 2050, from 15 per cent in 2010, while those aged over 80 to increase to 9 per cent, from 4 per cent. What it means to be “old” is itself complicated and dynamic; 65- year-olds are not the same as 85-year olds. The UN reckons the number of over-85s globally will between 2010 and 2050 grow at twice the rate of the over-65s, and 16 times that of everyone else.

Demographically, there are two Indias: one, a young India, 50 per cent under-25 and 65 per cent under- 35; the other, a soon-to-begin ageing India: the 2011 census counted those above 60 to be around 110m. The old are becoming the new thing. Longevity is making good business. As Robert McCrum argues in his Every Third Thought: On Life, Death and the Endgame, baby-boomers live in a “fantasy of immortality”.

The older olds are often wealthier, also healthier, with greater readiness for self-indulgence. “Retirement used to be a brief period between cruise ships and wheelchairs, with a bout of norovirus”, maintains Director of the MIT AgeLab, Joseph Coughlin; now it has become a complete new stage of life, as long as childhood or mid-life. He has found that people past 50 control 70 per cent of US’s disposable income.

“Marketers present these years as filled with golf, cruises and a rocking chair”. Boston Consulting Group calculates that some 15 per cent of firms have developed a business strategy focused on the elderly.

The over-60 constitute the fastest growing group in the populations of rich countries, their numbers set to increase by more than a third by 2030, from 164 to 222 million. They currently spend some $4 trillion a year and the number will only grow. A Humboldt State University economist, Erick Eschker believes that each American born in 1945 can expect nearly $2.2m in lifetime net transfers from the state – more than any previous cohort.

A report by McKinsey Global Institute finds older consumers to be an engine of growth in an otherwise sluggish global economy, pensioners in the rich world spending an average of $39,000 on consumption vs $29,500 for those in 30-44 age group. Most people accept that death and taxes are inevitable. As a good accountant can help with the latter, the usual prescription for the former is to avoid excess. Scientists at the Institute of Ageing Research at the Albert Einstein College of Medicine in New York maintain that generalised ageing process can be modulated with drugs.

The Methuselah Foundation, an ageing-research charity, claims that “longevity escape velocity” will enable man to reach the point where life expectancy increases by more than a year every year. Nature carried a report by David Harrison and his colleagues at the Jackson Laboratory in Maine on the life-prolonging effects of a drug called rapamycin.

A company, Sirtris Pharmaceuticals ran trials of drugs that affect proteins called sirtuins—a group of enzymes experiments of which on invertebrates show extending the lifespan. Medicine also offers the old running repairs; a world in which getting fitted with a new heart, liver or set of kidneys, all grown from one’s own body cells, is projected to become as commonplace as knee and hip replacements are now. If a body part wears out, it will be repaired or replaced altogether.

Smith & Nephew, a large European orthopaedics group, has had steeply rising sales of hip and knee replacements. Stem cells play an important role in the repair and regeneration of tissues. Many stemcell therapies are moving rapidly towards clinical trials under the rubric of “regenerative medicine”.

All sorts of products that promise to hold back the years are pouring on to the market: hair colours and antiwrinkle creams, Viagara and hormone-replacement pills, exercise machines and travel catalogues. For example, Nestle is pioneering a marketing strategy around skin care, banking on millions of longer-living customers wanting products like its Cetaphil lotion to reduce redness and itching.

L’Oreal recruited an old French actress Catherine Deneuve to promote its hair care products, while Estee Lauder hired Karen Graham to be the face for a new cream for the mature market. Unilever launched its Proactiv spread which reduces cholesterol.

Kimberley-Clark has overhauled its Depend brand of adult nappies to make them more like regular underwear. Sabi, a design company produced walking canes in bright colours. Electronics makers are producing devices that are designed specifically for old people.

The Japanese telecom firm NTT DoCoMo launched a new mobile phone called Raku Raku, or ‘easy-easy’ with large buttons and easier-to-read figures on the panel. Package-goods firms are printing larger typefaces. Ford created a “third-age suit” for car designers to wear, to help them understand the needs of older people: the suit thickens the waist, stiffens the joints, and makes movement more cumbersome. Thick gloves reduce the sense of touch and yellow-tinted goggles simulate eye cataracts. Growing consumption by elders is likely to favour personal services over manufactured goods.

As the senior population grows, cruise lines and other travel services will thrive, as will businesses that build, sell, or manage mobile homes, second homes on golf courses and in mountain resorts, downsized, all-amenities condos near major cultural centres and, of course. assisted living and nursing-home communities. In the 1950s-1960s, Americans flocked from cold industrial cities such as New York and Chicago to subtropical Florida.

Now the Chinese are seen moving from the industrial heartland in north-east to Hainan in the south. As happened in Florida, a retirement business has been built on the back of Hainan’s tourism. Sanya, a small fishing village in Hainan, until recently, is now full of high-end luxury resorts. Japan’s funeral industry and other companies have seized a rare growth sector – end-of-life businesses offering alternatives to costly temple gravestones, such as scattering loved ones’ ashes in Tokyo Bay.

Technology companies such as Yahoo Japan launched Yahoo Ending, a service that charged Yen 180 a month until one died, then sent an e-mail alerting friends and family once one reached the other side, smoothly closed one’s internet accounts, and set up an online memorial page, also offering to arrange funerals, complete with a Buddhist priest.

Humanity seems to avoid the trap fallen into by Tithonus, a mythical Trojan who was granted eternal life by the gods, but forgot to ask also for eternal youth. To get over the scourge of loneliness, that gnaws the elderly in their 80s and 90s, even a known staid and prudish India caters for romantic retreats such as Thikana Shimla near Kolkata and Vina Mulya Amulya Seva in Ahmedabad, which enable old senior citizens to forge new companionships.

Boredom, and the need for variety, would alter family life too. The one-partner life is already on the decline, could become rare, replaced by a series of relationships. Lynda Gratton and Andrew Scott reveal in The 100-Year Life that Americans over 60 are now getting divorced at twice the rate as they were in 1990, and Britons at three times.

“There’s more fun to be had after 50”, proclaims an online companionship site, Stitch, adding that “it’s all very safe”. With ever new challenges to face, the aged find plenty happening to let them conquer inertia and dullness, echoing Robert Browning: “Grow old with me! The best is yet to be”.

(The writer is Senior Fellow, Asian Institute of Transport Management and former CMD, Container Corporation of India.)