Regarding female fertility, this report from Norway outlines the trend that I vaguely thought was representative of most of the developed world over the last 100 years.
Female fertility is trickier to measure, since female fertility and age are strongly correlated, and women have been having kids later, so it’s important (and likely tricky) to disentangle this confounder from the data.
To be sure, I’m not an expert on the topic.
Declines in male fertility I think are regarded as real, though I haven’t examined the primary sources.
Regarding female fertility, this report from Norway outlines the trend that I vaguely thought was representative of most of the developed world over the last 100 years.
Female fertility is trickier to measure, since female fertility and age are strongly correlated, and women have been having kids later, so it’s important (and likely tricky) to disentangle this confounder from the data.