This percentage has been very stable for generations. Yet the distribution of income is not so stable, and inequality of income and wealth have been increasing for roughly three decades.
Incomes are unequal for many reasons, and some inequality is both inevitable, and reasonable.
Earnings vary over the life cycle, some are more willing to make heavy sacrifices of leisure to earn higher income, etc. But rising inequality causes various observers to express concern. Be prepared to discuss reasons given for such concern. The text presented the frequency distribution of incomes as a graph. Know the difference between mean , median , and mode .