Here is some science fiction, using just a pinch of economics, a dash of demographics: it is the year 2030. There are now twice as many old age pensioners as there were 30 years ago, they are politically organised and vote en bloc. They are living longer, and the State must spend vast amounts on expensive, high-tech health care, as well as on pension payments. To pay for this, the dwindling proportion still at work is heavily taxed. The taxpayers resent it, bitterly.

Not so much fiction as mathematics.

The ratio between economically active people and retired people is going to reduce radically, says Ms Anne Maher, chief executive of the Pensions Board. "At the moment there are five people economically active for every one retired, and that's going to drop to less than two people economically active for every one retired by the middle of the next century."

What happens next, she says, is pretty clear: "That obviously means that either the people paying in will have to put in more, or the people who are drawing out will get less."

In fact, the Republic is in better shape than the rest of the European Union. By 2030, the Irish ratio of those over 65 to those between 15 and 64 will be 25 per cent; that is, for every four workers there will be one old person. But in Germany, the ratio will be 49 per cent, in Italy 48 per cent, in Spain 41 per cent and in France 39 per cent. The EU rate as a whole will be 40 per cent.

Some countries are already trying to cut back on the amounts they will give to pensioners. By next year, Italy will increase the male retirement age from 63 to 65, and the female from 58 to 60. In Austria, Belgium, Portugal and Britain, governments are increasing the retirement age for women to the same point as for men. Many more are cutting back on early retirement provisions, effectively keeping people at work for longer.

The Republic has had, by European standards, low levels of social welfare promises, and relatively high levels of private pension provision. But if the economy and the European Union continue on their current paths, the Irish will be, by 2030, living in a wealthy State in an integrated political union. Could taxpayers in the Republic be forced to subsidise the elderly in the rest of the EU?

Under current EU agreements, this could not happen, but few would argue that over the next 30 years there will be no new treaties.

And even if the Republic does not have to share its relative wealth directly, its people and businesses will have to pay interest rates driven higher by the borrowings of Germany, Italy, France, Spain, the Netherlands and others.

But pensions are the easy part of the ageing population problem. Health care has the potential to become a bottomless money pit, and a push-button, emotional issue like no other.

"The balance of evidence suggests that older people as a whole may account for 30 to 40 per cent of all health care costs," the OECD said in a recent report, Maintaining Prosperity in an Ageing Society. As health care already accounts for around 8 to 10 per cent of GDP, even a modest growth in health care costs would imply a significant pressure on public finances."

The dirtiest job in the health care business has always been that of deciding whether an operation is worth the cost for a particular individual. For example, is it worth carrying out a hip replacement operation for a 60-yearold? A 75-year-old? A sprightly 83-year-old? A 90-year-old? What if the 90-year-old has paid into the VHI all his or her life and feels entitled to such an operation? What if the 90year-old has not paid any private health insurance - should he or she be treated less favourably by the health service?

The problem is that health care, even without the increased numbers of elderly patients, is becoming more and more expensive. The new, live-saving equipment and drugs we read about in the newspapers cost vast amounts to develop and manufacture.

According to the OECD report: "Older people quite naturally tend to seek access to the latest medical technologies as a way to prevent or delay the onset of chronic conditions and disabilities. The fear would be that older people would therefore provide a new market where an excess of specialised providers could find a use for newly developed, and expensive, technologies with gains to health status that remain to be assessed in terms of cost-effectiveness."

Not only will there be more patients, they will be living longer. In fact, life expectancy is rising quite rapidly: Irish men are now expected to live until 77, women until 81. By 2019, the average for men will reach 79 and for women 84.

"And if people are going to live longer they are possibly going to have a longer period when they are going to require long-term care," says Ms Maher.

At the moment, 80 per cent of carers are women, and many are voluntary or badly-paid. With more Irish women entering the workforce and seeking properly-paid jobs, the issue could easily snowball. The Ireland of the next century could be a country of conflict between the generations.

Retired people - the employees of today - may feel that they have worked hard all their lives, already paid in effect for their parents' pensions and health coverage as well as their own, only to see their incomes, social services and health care slashed back anyway.

Our children and grandchildren - could take the view that they are being forced to work longer, pay more tax and higher interest rates, to keep a bunch of cosseted fossils hogging the already-clogged golf course and using the latest, over-priced, medical technology to prolong lives beyond their natural end.

With the elderly already forming a powerful lobby in some countries, such as the US, Irish elections, instead of being fought on party lines, could be won or lost on who appeals most to the over 65s.