Some of the calculations they made were utterly bizarre. Like assuming the child wasn't paying anything forward until "retirement" of the parent. All adults being net positive is not the same as the elders not benefitting from in-kin capture of investments in a scheme that almost resembles taxation moving benefit upwards in in-kin seniority.

So if you were living in an agricultural society, you would trust their financial instruments and institutions governing land ownership more than you would trust your own family? Really?