The corresponding Gini coefficient, labeled G, is the concentration ratio applied to income distribution and is defined as:
(6.3)
Re-arranging and simplifying the terms yields a coefficient depending only on the parameter δ:
(6.4)
Clearly, the α coefficients will be used again to compute the Gini coefficients as δ = 1 – 1/α. As there are as many α coefficients as income brackets, we are able to average a value of α for each state in each year.
We now turn to the application to the United States from 1965 to 2003.