I don't know how to put this in a formula, but my observations about my family's wealth disappearing is the following:

Great grandpa had tons of land, dies and leaves it to his children who then left it to their children when they died to split as heritage (so my parent and uncles and their cousins) which they ended up selling and splitting it between around 60 heirs. They bought things that are not really an investment like cars, new furniture, vacations...So all the wealth from my great grandpa has vanished because his great children like to spend money rather than invest.

Edit: typo.