I found one (generally) related past thread - have there been others?<p><i>Birth Order Effects Exist and Are Strong</i> - <a href="https://news.ycombinator.com/item?id=16104491">https://news.ycombinator.com/item?id=16104491</a> - Jan 2018 (193 comments)
Birth order is the only thing I truly believe it. It explains so, so much about people. Sure there's the 15-20% outliers, but overall -- it is spot on.
The graph on p198 seems pretty surprising to me. Though I didn’t read the accompanying text or look for original sources. It just seems pretty implausible looking at it.