There are two aspects to this: firstly that fertility rates in the “developed” world are declining and secondly (and most importantly) fertility rates in the so-called “developing” world are still alarmingly high. The report makes this comment:
“Without migration, countries will face ageing and shrinking populations”
Taken alone that remark tends to suggest that the ideal scenario is for the developing world to continue to churn out children that it cannot sustain so that those children - if they survive - can migrate to the developed world to tend to their “declining and ageing” populations. Right. I hadn't thought of that wheeze.
The world needs to develop economic models which do not depend on a continually increasing population. Ideally they need to work on steady or slowly declining numbers for at least a century or two. To say that populations must continue to rise to cope with those getting old is the logic of the madhouse. Countries such as the UK are already struggling to properly sustain the populations they have (and by sustain, I don’t mean just food and drink, but a decent quality of living). Much of Africa and Asia will never control their populations and all the rest of the world needs to do is to prevent vast numbers from those countries attempting to migrate “for a better life”. They should remain where they are and seek to improve the conditions for their descendants as people in the developed world did and continue to do.
“//Except for some countries who have high fertility rates, notably across Africa, Asia.//
These also have higher infant deaths”
Quite so. But excusing the unsustainable population growth in such places on that basis (where children have a high probability of failing to survive to adulthood mainly because of the conditions they are born into) is rather like encouraging cats to have more kittens because many of their offspring end up in a sack at the bottom of the canal.
“Every country runs an enormous debt against borrowing. If there are less working age people, the GDP falls meaning the debt is less serviceable. Pension pots become severely affected (depleted) and so the elderly are a greater burden on society through benefits. It's quite a viscous circle.”
But not quite as vicious a circle as suggesting that more young people are needed because there are more older people to look after. Incredible as it may seem, the young carers eventually get old themselves - and, guess what? They need even more young carers to look after them. And guess what happens to that latest batch of “young carers”? (I'm sure you get my drift).