writer here. I do mention housing costs specifically as being a probable large factor, as well attempts at financial pro-natalist policies in Europe. I recognize the data you share above, but it's not clear to me that that any solution can come from economic policies alone. After all, the places that have the most children today are very poor with far more uncertain futures.
That said, I'm certainly not an expert and this is a very complex issue. My main goal in writing this was to spark a conversation and get people thinking about this. Would love to hear your further thoughts.