Ageing may mean several different things. I thought I’d write a short memo to describe what it means when someone says that societies are demographically ageing.
1. Declining fertility
As opposed to what may seem obvious, babies are an essential driver of ageing, or more precisely, the absence of babies. When people have fewer children the balance of age groups in the population changes and the proportion of children diminishes. As a result, the average age of people tends to increase.
Declining fertility is the main driver of the demographic concept called the demographic transition. However, according to this theory, infant mortality rate declines before fertility rates, which leads to an increasing number of children during the time of the transition.
2. Decreasing mortality rates
Despite having very low birth rates in Europe, we still speak of the ageing of Europe. This demographic evolution is associated with the second main factor for ageing, i.e. decreasing mortality rates. People start dying later than before. Instead of dying at all ages due to a number of varying causes, especially infectious diseases, people pass away at more advanced ages, usually caused by chronic diseases, such as heart or respiratory conditions. This evolution of the causes of death from infectious diseases to chronic diseases is usually referred to as the epidemiological transition. The ageing of Western Europe is essentially due to the decreasing mortality in old and very old people. The groups referred to as the “oldest old” (85+) and the centenarians (100+) are the fastest growing age groups.
Note that debates in France notably around the fear of exploding costs of ageing are associated with the ageing of the baby-boomers (those born between 1945 and 1965) rather than ageing in general. This phase is temporary due to the unusually high birth rates combined with unusually high children survival rate during this period. The impact of this demographic bump will progressively fade away throughout the century and Western countries may even become slightly younger at one point. Society will nevertheless have to bear the costs of this populous generation. Other things being equal, Western societies will remain “old societies” where people have few children and nearly all live for a very long time.
In sum we are transferring from two demographically sustainable systems: in the first one, many children are conceived but few live to old age, while in the second one, few children are born but nearly all live to old age. In Western Europe, the transition is nearly complete. The question relative to whether the current number of people on the planet assuming a decent standard of living is sustainable is a completely different question that is unrelated to ageing. To me, and to many others, the advanced ageing of Western Societies is one our greatest achievements that should be protected.