I don't have statistics, but a fun factoid is that the Grosvenor family, who own many properties in the west end of London, were originally granted those properties because the grantee was the grand-nephew of William the Conqueror. So wealth can last a long time. For those families who are luckiest and canniest, the only major threat is social breakdown as a result of revolution or being conquered.
> Even with wealth evenly split between each generations kids
This is why primogeniture and entailments were invented. They were necessary to maintain dynastic wealth. In cultures where partible inheritance is more common, such as the US, dynastic wealth has a much shorter half-life.
The author shows numerous examples but one of the most striking for English-speakers is that the Norman conquerors of 1086 are still, 31 generations later, over-represented at places like Oxford and Cambridge admissions and upper class probate court records.
I'm curious what the statistics are for a family remaining wealth over a long period of time.
Even with wealth evenly split between each generations kids, given a growth of just 4% it might end up with each generation getting a greater amount of wealth still.
In the past large familes prevented this, but if the average extremely wealthy person only averages 2 kids. The dilution through children just doesn't occur.