10. 11. A key driver of income inequality since 1980 is the share of wages in the incomes of the richest 1% of the population. Vollrath attributes most of the slowing of per capita income in the 21st century to slower growth of physical capital per person. The aging population in the U.S. can be interpreted [as Vollrath does] as a sign of economic success in the 20th century, especially for women. Empirical evidence suggests that states with lower income tax rates and / or fewer regulations on business are richer and grow faster than other states