> We're about to hit increasingly aggressive competition both to hold on to people, and to attract immigrants as more and more countries start getting bitten by demographic shifts.
This has an implied assumption that either more population is always better or that for all of the countries the current population is below the optimum level.
What if for some countries the best population size - the one that provides the best quality of life for its citizens - is close to the current one, not larger? What if for some countries the most favorable population size is below the one they currently have?
It has the implied assumption that a functioning economy is linked strongly to the number of people of working age relative to the number of people outside it, and part of the population decline comes with an inversion of the population pyramid where an increasing proportion of the population is retired.
As such, even if there is a "best" population size below the current population size, you will face massive upheaval if the decline toward that size isn't happening slowly enough that you can offset that either with technology, temporary workers, or just grit.
You also have no reason to assume the drop will stop at whatever level you want, and so you will see even countries where people do think some reduction is fine start to aggressively compete to hold on people or attract immigrants at whatever level they feel will give them a soft-enough landing and then stabilization.
E.g. you can look to Italy over the coming years. Italy is already in population decline, yet has a government many consider far-right and anti-immigrant - clearly, Italy is not ready to loosen up immigration to stem it yet, and is willing to accept even increasing the rate of its population decline while trying to address the underlying fertility rate.
Personally, I expect to see a major change in policy from Italy once this really starts to bite, but their current unemployment rate will still buffer them for a few more years (and once it drops, it might well create a slight rebound, but even if that happens, it's unlikely to do more than slow the decline slightly, and won't address the labour market for more than two decades).
If I'm right, you should start to see the tone change once the unemployment rate drops a bit further and pressure from businesses in need of labour starts affecting Italian politics more, followed first by increased attempts at appealing to European migrants first, with e.g. tax breaks and the like, before they eventually give in and start rolling back the restrictions on non-EU migration.
This has an implied assumption that either more population is always better or that for all of the countries the current population is below the optimum level.
What if for some countries the best population size - the one that provides the best quality of life for its citizens - is close to the current one, not larger? What if for some countries the most favorable population size is below the one they currently have?