Income, or wealth, inequality harms both the rich and the poor by limiting the spectrum of lives to which they are exposed to each extreme. Assume a society that involves persons R and P who are equally talented and passionate but from, respectively, rich (top 20%) and poor (bottom 20%) families; and that every single person in the society desires only to climb up, never down, social as well as economic ladders. Then, the life spectrum one ever experiences is limited to 20% for R and 80% for P if they never interact and 80% for both if they fully interact as R learns from P indirectly lives of the middle 60%. The merits of exposure to a wider spectrum of lives is obvious. For R to sell products as a businessman or win votes as a politician, for example, she must understand what the bottom 80% care or concern about and suffer from. Hence, the more the interaction between R and P, the wider the spectrum to which R and P are exposed, the more the value created by R and P, the richer the society. As the income or wealth equality narrows the distance between R and P, and the wealth of the society is a function of the interaction between R and P, which in turn is a function of the income or wealth equality, it is straightforward to conclude that the less inequal the income or wealth is, the richer the people are in this stylized society.
Takeaways from this society setup include 1) the importance of lessened inequality, which generates more within-society interaction between the rich and the poor, for economic growth; 2) the importance of indirect learning of lives from different economic classes through reading classics and extracurricular activities at school; 3) the risk of firms hiring talents from rich families having a record of little contact with the bottom 80%.