Now we are all going to live over 90, we need to look to Japan for some advice

It’s a standard after-dinner quip, attributed among other people to Nubar Gulbenkian and Maurice Chevalier. When asked what he thinks of old age, he replies, “It’s fine when you consider the alternative.”

The new study by Imperial College, published in The Lancet, projects even longer lifespans than previously estimated, with South Korean women born in 2030 living to an average age of over 90. That should sharpen all our ideas about how to cope with ageing populations. If there is a crisis now in the UK with social care for the elderly, think what it might be like in another couple of generations’ time.

It is an issue we are all aware of, but such a huge one that it is quite difficult to break it down into bite-sized chunks. So here’s a structure to think about it.

The first and most important point is that this is not a problem. It is something to be celebrated that children will know their grandparents and maybe great-grandparents – and vice versa. The fact that people can live more healthy lives as well as longer ones is to be celebrated too. There are a few countries in which life expectancy is falling, among Russian men for example, and they are not to be envied. But it follows that the whole world has to adapt and some societies will adapt better than others.

The next point is that adapting is both a financial and a social issue. The financial aspects look harder but may turn out to be easier. The key financial problem is that the western social welfare model, whereby each generation of working people pays for the previous generation’s pensions and social care when retired, was designed for quite different circumstances. Life expectancies were lower of course, but also it was designed for rising populations. If the size of the workforce shrinks not just in relative terms but absolute terms, as it is in many European countries now (though not the UK), there simply aren’t going to be enough people of working age to pay for the previous generation’s needs.

There are two ways in which countries can adapt. One is that people save more when they are earning. In a way it does not matter whether this is done through taxation or through personal savings, though if you are asking people to forego current consumption for future protection it is probably politically more credible to go the savings route. (Tell people that National Insurance Contributions go to the previous generation’s pensions, not their own, and they will get the message.)

That has to be done. We have to save more. But this is not just a financial issue, for it is also a social one. Having savings is no help if there are not the people to provide the services. So somehow western societies have to find ways of enabling a smaller workforce to care for its older people.

That leads to the second way in which we will have to adapt. Part of that adaptation is that we have to work longer. This is easy to say but hard to organise. There are some activities, let’s include journalism, where people can go on working beyond normal retirement age. But there are others, such as construction, where you cannot reasonably expect people to work into their 70s. So the task facing society is not just to improve pensions and social care, but also to create a more balanced working environment, where people are nudged towards doing whatever work they can do, paid or unpaid, beyond what will inevitably be an increasing retirement age.

This is easier in a cohesive society than in a fractured one. Japan has the greatest problem (or greatest benefit) as an ageing country. It is not only the oldest society on earth now. It is the oldest our species has ever known. So the young old – those from 65 to 80 – care for the old old – those above the age of 80. Japan does provide some sort of model for the rest of us.

There is a further twist. What most people would desire is not so much longer lives but longer active lives. Here health care and personal behaviour have a huge role to play. Countries that have good health care are likely to experience greater longevity. South Korea and Japan are good examples of competent and not particularly expensive health care. But individual habits matter. One of the reasons for rising longevity is that people are stopping smoking. One of the reasons why it is not climbing as fast in the US (and to some extent the UK) as elsewhere is poor diet and the rise in obesity.

This heads into a difficult area. To what extent should societies be bossy? And will they be effective if they are? But you see the big point. These are issues for all of us. The prizes will go to those that manage these best. And this report helps us appreciate both the scale of the task, and of the prize, ahead.