The OECD report's light on demographic data, so here's some additional context courtesy of BirthGauge on Twitter. He has somewhat of a following, so his replies are generally filled with people posting more frequent updates from national or subnational authorities reporting their demographic statistics.
I'll be posting some of his tweets and retweets over here for their data.
Here's his summary of up-to-date births and TFR estimates, with Europe on the left and then a selection of countries from the Americas, AU/NZ, and Central/East/SE Asia on the right.
Some of the countries he forecasts will have a lower TFR than Japan this year include Thailand, Costa Rica, and Chile. These are not (yet) developed economies, but they will be an interesting watch over the medium term as they will approach the demographic character of developed economies in Europe and the Americas.
While the OECD report makes a big deal out of childlessness, that explains only part of the the decline in birthrates. To get a clearer look, we can use Birth Order, which is closely correlated to the TFR. By using this metric, we can see the differences between how countries get their births (e.g. low childlessness but a large number of small families or high childlessness with more larger families).
Birth order helps explain how countries' TFRs change over time.
Can you see where the postwar Baby Boom was for the US? That helps explain how the post-WW2 Baby Boom came to be.
Speaking of historical baby booms, taking infant and early childhood mortality into account shows that decreases in births were offset by advances in medical care in modern times.
We can use another metric, cohort fertility, to figure out trends (e.g. are women simply postponing having children?).
Lastly, some more selected tweets showing data on a more granular level than nation states:
...with metropolitan areas generally having depressed fertility compared to the countries they belong to.
And now, a more tangible representation of the effects of declining birthrates: age pyramids.
Please guess which of these age pyramids is going to have to increase retirement ages or slash pensions or both.
This has been quite the data dump, so I'll just close this post with this tweet that coincidentally summarizes my thoughts on the discussion in this thread.
Let's say that, at the level of a country, size matters.
Great post, the vast majority of the world is decreasing their TFR without increasing their Human Development Index at the same pace, in my country Brazil, we already had to do a retirement pension reform because not only is a ponzi scheme like most pensions around the world, the TFR has gone below the replacement levels in 2005 and we are en route to a population decline in the next 10-15 years, even in poor and uneducated regions you have 1-2 children in contrast with what used to be much higher. I think only Malaysia, Thailand and Chile could become developed without reaching the population decline, unfortunately many will be old and poor.
Outsider cases to the rest of the world are USA where i've noticed that families with 3 or more children are more common and indeed proved by the data above, Israel, and former URSS and their allied states. In the case of Israel, Haredis are responsible for most of the births, the non-haredi jews and arabs have a TFR around 2.7, in the case of the former it could be by religion, the latter two, by war scars. In case of eastern europe, there was a major emigration and population decline with the fall of communism in 89-91 and only by 2000 saw many returning to the homeland and an economic prosperity.
As stated in the first few tweets, the fertility rate worldwide was already falling pre-WW2, the war itself caused a incentive to many to marry and have children as quick possible because they were afraid of being killed without successors, after that the major economic prosperity in turn made having children cheap as buying something. The reason why TFR was falling before that is because our living standards were getting better over the years alongside cultural changes, cheap labour and survival were two reasons why children were being born before that.
Fast forward we have numerous programs in developed countries to increase the TFR, but it has come to little, you can have a few years of increase then it all goes back to where it was before, its not just financial reasons, its also cultural, you have people who doesn't want children, others who want to settle with just one, even if they had the financial means to have more. Another very important thing that is forgotten to be told is that you need two, not one, children to keep the population level, which is a very hard thing to expect from anyone.
TL;DR: Its not just economical factors, but societal-cultural ones that play a equal role. A poor family in the 60s and 00s would have children regardless of the challenges, now the same challeges today are unnaceptable to be dealt with. The economic prosperity from that time even if its repeat today might not bring the same TFR increase.