There is then a middle passage where rising economic conditions make lower fertility usefully sustainable, with moderate inflationary immigration into the economy.

But then you hit Japan, and without significant re-appraisal of how economics work to national advantage, your need for replacement labour to manage the growing old population in decline is a huge burden on the tax base.

So this take, is interesting because it seems to invert some of the logic here. It seems to imply, because its economically advantageous, people observe it and stop having so many babies. I thought it was much more that high birthrate was driven in high childhood mortality, and economic necessity of subsistence farming.

I'm also a bit surprised this is worthy of note, because surely the persisting decline in Korean and Japanese birth rates measured over decades signalled this .. well decades ago? Isn't this trend now firmly established in most of the developed G20 class economies? Poland might be a catholic nation but like Ireland continues to be below replacement rate.

The French tax break was for ludicrously large families. like 5 or more. You'd be wrecked.

Not a demographer or a statistician or an economist, which will be obvious to all three reading the above.