[Terr_]

A few more bullet points on the pile that aren't as often discussed, probably because they don't fit grand moralistic/child-rearing narratives:

* Regression to the mean. [0] Humans try very hard to avoid "dumb-luck" in any story even if it's the best available explanation.

* Inheritance split to more than one heir.

For the heir-scenario, imagine that Generation 1 is a single family living off the interest of $12m. They have three kids, who marry equivalently-wealthy spouses. Now Generation 2's average wealth is $8m. That's a decrease, and we haven't even begun to talk about factors like "raised with good habits" or "work" etc.

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[0] https://en.m.wikipedia.org/wiki/Regression_toward_the_mean

[Terr_]

To digress a little on the "dumb luck" stuff... Human brains seek patterns and create stories and "find" cause and effect, and that's been extremely useful for us overall... But there are also risks and blind spots.

My favorite example is the humble coin toss. Yet many people joyfully fall into faux-explanations of "hot streaks" or "overdue" outcomes etc., and retain them no matter what statistical evidence you provide.

Even those who consciously reject those ideas still have to bat the intrusive thoughts away, and that's for one of the most well-studied statistically characterizable things out there.