This is typical of soft science papers in economics. Authors haven’t explored major aspects and clearly they had some prior beliefs and went after it. For example, when capital stays in the hand of few, it also means wealth accumulation happens much more rapidly at the top. In capitalistic society, not having capital means significant portion of your earnings is returned to someone else who is targeting passive income. When you go in the mall and pay $100 for a dress, $10 goes to someone who simply is owner of the mall and rarely visits it if at all, another $10 goes to owner of factory who never works there but has legal titles, another $10 goes to owner of farm that produced cotton but never put sweat in that farm -and so on. A vast majority of your purchase price ends up to rent seekers one way or another. This is why rich becomes richer.