I've just bought my mother the same dress I bought myself last week. It's a shimmery, spaghetti-strapped shift - not the sort of demure garment you'd conventionally expect a 55-year-old woman to wear. But my mum is of that generation that has made a career out of defying convention. And thank God for that, because now growing old doesn't seem half as scary. In fact from where I'm standing it looks positively attractive. The baby boomers - that me-first generation that invented the teenager - are about to reinvent retirement. My mother and her friends display absolutely no enthusiasm for traditional grandmotherly activities like babysitting or rocking in a chair crocheting scores of decorative doilies. Instead they're growing old disgracefully, wearing thongs on the beach, mini-skirts in the boardroom and treating themselves to massages, champagne brunches and weekends away. Their hedonism goes hand in hand with a spend, spend, spend mentality. In modern post-industrial nations the over-50s are the richest section of society. In Britain they hold 80 per cent of the wealth. They buy more Porches and rock music than the under-30s. Always radical, will the baby boomers now hail the end of ageism by defying the stereotypes of what it means to be old? They certainly seem to be changing perceptions of ageing. It no longer has to mean creaking joints, low energy and reduced libido. Like recycled teenagers the older generations are displaying a breathtaking zest for health and fitness. The veteran categories of sport such as swimming, cycling and running are swelling. While the girths of their grandchildren expand on a junk food and couch-potato lifestyle, the baby boomers are hitting the hills and the treadmill with gusto. Prolonging their youthful looks is another enthusiasm. High divorce rates means many in their 50s are looking for new partners and are prepared to spend generously on their appearance, reinventing themselves as youthful, hip, go-getters with more cash and panache than their younger rivals. Consumer culture is so focused on youth that we rarely give a thought to the over-50s. Advertising targets the young. Models are dumped in their 30s and 40s. But marketing men will have to redefine their view of older people as semi-handicapped. Ageing boomers will not stand for being overlooked. Women like Sophia Loren and Jane Fonda are proving that being older doesn't necessarily mean being part of the wallpaper. Ageing has been redefined as nothing more than a transition to a new life. Men too, by choosing to date women in their 40s and 50s over young babes in their 20s, are helping to change the common perceptions of older women as sexually past it. The English actor Ralph Fiennes caused a stir when he walked out on his young wife, Alex Kingston (of ER fame) for Francesca Annis, 17 years his senior. Almost a third of unmarried women in the United States aged between 40 to 69 are dating younger men. More surprising is the news that there is still sex over the hill. Not only are women fessing up to a bit of nooky in their 80s, but according to the The Sunday Times newspaper there is a 'growing belief that they are built to enjoy sex and orgasms more as they get older'. Ten years ago, sex researchers Samuel and Cynthia Janus discovered that women over 65 were having more sex than those aged 18 to 26. And if they're not quite feeling up to it, testosterone shots will provide an instant libido boost for post-menopausal women. The 21st century is beginning to look like it might be the best century so far for ageing or, at least, keeping its negative implications at bay. Drug companies now see an ageing population as their new big market. Millions of dollars are being spent on research into the diseases of ageing like Alzheimer's, arthritis and flagging libido. As we live longer and grow more affluent, new pills, potions and exercise regimes will help us hold back the years. We are living 30 years longer now than we were a century ago. And although forecasters see the glut of oldsters as a drain on the economy and health-care systems, it may actually hail the dawning of a new kind of society, one in which the voices of retirees are no longer ignored and their wisdom and life experience are utilised. As mentors, volunteers and role models older generations represent a mine of untapped social potential. Although many say they can't afford to retire many others simply don't want to - particularly those running their own businesses. Rupert Murdoch, Alan Greenspan and several Hong Kong tycoons show no sign of letting up. The baby boomers are better educated and more adventurous than any generation before them. They choose jobs and careers they find personally fulfilling and see no reason to stop when they reach 65. Suddenly, knitting their way through retirement doesn't hold the attraction it did for gran. Whatever the economic implications, we'd better get used to having oldsters around because pretty soon they are going to outnumber youngsters. According to the United Nations Population Division the number of infants in the world will begin to shrink within 10 years. All future population growth is expected to come from older people living longer, healthier lives. By 2050 there will be 35 million fewer children and 1.2 billion more people over 60. China's total population could be less than it was in 1980 and 30 per cent of its population will be over 60. It looks like old might be the new young. Allison Jones is a Hong Kong-based journalist