Money income inequality in the USA is rock solid

Ten years ago we started modelling income inequality in the US using data gathered by the Census Bureau. Personal money income has been measured in the annual Current Population Surveys (CPS) since 1947. The CB counts populations in various income bins and publishes the distribution of personal incomes. Unfortunately for researches, only PDF scans are available before 1994. When these scans were still available, we downloaded them and converted into digital format.  These distributions allow direct calculations of Gini ratio. Figure 1 demonstrates that the level of inequality, as expressed by money income, is rock solid since the late 1950s. It oscillates between 0.51 and 0.52. This is the longest and most consistent time series of income inequality.

Between 1947 and 1959, Gini ratio grew. 

Figure 1. Gini ratio since 1947