For me one of the most compelling data points wasn't even a parenting reference. It was https://www.amazon.com/Millionaire-Next-Door-Surprising-Amer.... First published in the mid-1990s, the chapters on the children of millionaires found that the more support millionaires gave to their children, the worse that those children turned out. Armed with that theory, I've always doubted the wisdom of extreme helicopter parenting that has become popular since.