IN MUCH of the rich world 65 still marks the beginning of old age. Jobs end, subsidised bus travel begins and people start to be seen as a financial burden rather than an asset to the state. The larger the “65-plus” group becomes, compared with the population of working age, the more policymakers worry about the costs of their health care and pensions. By the end of the century the “old-age dependency ratio”, which tracks this relationship, will triple. Pessimists predict a “silver tsunami” that will bankrupt us all. But does it still make sense to call 65-year-olds “old”?

The Oxford English dictionary defines “old” as “having lived for a long time”. It illustrates the sense with an accompanying phrase, “the old man lay propped up on cushions”: the old person as one who has made all the useful contributions he can possibly make to society and is now at rest. When pensions were first introduced in Prussia, in the 1880s, this was probably a fair characterisation for anyone over 65. Not many people lived beyond this age; those who did were rarely in good health. But today many 65-year-olds are healthy and active. Donald Trump (71) may be many things, but old he is not, nor for that matter is Vladimir Putin (64), who qualifies for his bus pass in October. Yet governments and employers still treat 65 as a cliff’s edge beyond which people can be regarded as “old”: inactive, and an economic burden.

This is wrong, for three reasons. First, what “old” means is relative. Life expectancy has gone through the roof since Otto von Bismarck pioneered the Prussian welfare state. Today the average 65-year-old German can expect to live another 20 years. So can most people in other rich countries, meaning old age now arguably kicks in later than before. Second, the term carries an underlying implication about health, or at least fitness. But healthy-life expectancy has grown roughly in tandem with life expectancy; for many, 70 really is the new 60. Third, surveys show that the majority of younger over-65-year-olds increasingly want to stay actively involved in their communities and economies. Few want to retire in the literal sense of the word, which implies withdrawing from society as a whole. Many want to continue working but on different terms than before, asking for more flexibility and fewer hours.

All this shows that life stages are primarily social constructs. Words like “old” and “retired” signal to policymakers, as well as to old people themselves, how they ought to behave and be treated by governments, businesses and employers. In a three-stage model of life’s cycle, children learn, adults work and old people rest. As a result, most institutions still treat 65 as a cut-off point for social and economic usefulness. But ageing is a gradual process, which people experience in different ways. While some may feel old at 65, nowadays most do not. Acknowledging that there is a new stage of life between full-time work and old age would help everyone make the most of longer life spans.

Dig deeper: Our special report on the “new old” explains how to get to grips with longevity