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I think there is an unwritten law that every article or policy discussion about the aging population must start with some scary statistic to get the debate going. So here are some from the UN. Between 2015 and 2050, the proportion of the world’s population over 60 will double from 12 percent to 22 percent. In 2021, there will be 17 people aged 65 and over for every 100 people aged 20 to 64 (this is the so-called “old-age dependency ratio”); by 2050, there will be 29 out of every 100.

So far, very familiar. But what if these statistics are not a useful frame for the debate? What if “65 and over” is a poor definition of “old age”? After all, what if chronological age isn’t a good measure of aging?

The only thing a person’s chronological age really tells you is how many years they lived. Policymakers are concerned with statistics like the above because they use chronological age as a proxy for other things they are concerned about, such as the number of frail or sick people in need of health care. or social care in the future, or the economic and financial impact of fewer workers and more pensioners, and so on.

That would be fine if chronological age were a reasonable proxy for all things, but is it? A ROLE published last month by economists Rainer Kotschy, David Bloom and Andrew Scott argued that reliance on chronological age is “at best incomplete and at worst misleading”, as it provides “only limited information part of the aging process”.

Most obviously, people of the same age can vary in how weak or unhealthy they are. Using data from the US and England on the physiological abilities of over-50s, Kotschy, Bloom and Scott found that the healthiest 10 percent of the population at age 90 had about the same level of frailty as the median 50 years old. .

Average levels of health and fitness by chronological age can also change over time. In the UK, for example, 70-year-old women in 2017 showed the same level of poor general health as 60-year-old women in 1981, according to the Office for National Statistics.

If you use chronological age as a proxy for when people stop working, that too varies from country to country and over time (and is, of course, highly sensitive to changes in the state pension age) . How meaningful is an “old age dependency ratio” that classifies those over 65 as “dependent” in a country like the UK, where their proportion in employment has risen from 27 percent in 2014 to 40 percent in 2024 ?

As Warren Sanderson and Sergei Scherbov, leading researchers in this field, placed it: “Should 60-year-olds in Russia in 1950 be considered as old as 60-year-old Swedes in 2050? If not, is there a better alternative?”

Sanderson and Scherbov’s proposed alternative is to define the onset of “old age” as the point at which you have 15 years of life expectancy left. Through this lens, the past, present and future look very different.

In the UK, for example, which enjoyed rapid growth in life expectancy until the last decade, the number of over-65s increased by 8.3 million between 1981 and 2017, but the number of people who have a life expectancy of less than 15 years fell. in 7.4mn. And if you will be recalculated Old-age dependency ratios with this definition of “old”, they are lower in all regions of the world except sub-Saharan Africa and Oceania (excluding Australia and New Zealand), and this is expected which rises less steeply.

Of course, that’s not the right lens either – it depends on the specific issue you’re concerned with. Asking when people will receive their state pension. In recent years there has been an increase in new “watches” which refers to measuring a person’s “biological age” based on metrics such as blood proteins. Could it be used one day to determine each person’s state pension age, because any system that uses chronological age or average life expectancy is unfair to poor people who live which is shorter life?

Scott told me he wasn’t sure people would accept that, even if the clocks turned out to be scientifically robust enough. “Can you imagine two people of the same age, same job . . . but one gets the (has a state pension) three years later?

There is no single perfect metric that can replace chronological age as a measure of population aging. But when you see the definition of “old” as something other than the number of years people live, it starts to look more convenient than inevitable, and those scary statistics about the pace of our aging as a challenge. rather than a destiny.

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