Seriously though, workers on what? I find it quite odd to base the value on workers as being a percentage of retirees, that's entirely detached from demand, productivity and opportunity.
"We need more workers to fund the old ones that stopped!" I get the basic logic, but it's stupid.
This is the unexamined premise that keeps on going unexamined. Europe makes less and less each day, growing more and more dependent on China for production (as on the US for security, although Europe seems a little less dependent on Russia for energy now). Automation fills the tedious, low-skill jobs that remain onshore, and the promise of industrialization, digitalization, and now AI is that fewer human workers are needed to sustain equal productivity. Why does the sane world that frets about offshoring and AI gutting employment also need unskilled immigrants to be "moar workers?"
Plus there are still gaps, things which cannot be automated or offshored, and many which will only do so after great effort. Lotta money to be lost there without bodies.
Having a large and rapidly growing underclass also sounds like an unhealthy demography. Immigration won't solve the problems facing France, it'll make them worse.
But anyway population fluctuates. These things tend to work themselves out normally when your main goal is the good of the nation and not just inflating the GDP as quickly and recklessly as possible.
A system that says "The number of working-age people must be at least 5x the number of retirees" is literally demanding unending (super)exponential growth. It's fundamentally impossible on a finite world. It's going to break down at some point. The only question is whether that happens before or after filling the developed world up with immigrants from the undeveloped world.
If not. difficult to solve?
I have no strong opinion to the question of contraception but it would be sensical to promote and educate people (both men and women) that parenting is good (arguing with nature is hard) especially when the nation needs more births.
I feel obligated to apologies, but won't. I do accept to having to point out I'm in no way stating contraception should be illgal or anything of that sort.
I concede that for solutioning the short term issue of shortage of workers, there are no other scheme to employ, I'm out of idea. No wait! There are officially almost 3 million unemployed residents in France. I won't try to demonstrate it's in fact double this number, nor bring up the argument a few million don't really work given they do just as little as they get paid.
We are taken for fools. And a number of idiots found no alternative than setting stuff on fire. It's not just immigrants rioting.
This means when someone is in their mid fourties and will retire in 20 years, someone needs to give birth to a child so that it will grow up and start working just in time for the retiree. If children get born too early, then you run into the problem of them needing their own caretakers. These children don't compensate for someone else leaving, so they add to the population and their future caretakers will also add to the population leading to an exponential Ponzi scheme.