Measuring Income Inequality: The Journey from Relative Mean Deviation to Gini

In the history of development of ideas about measurement of income inequality three measures viz., Relative Mean Deviation R, Relative Mean Difference D and Gini coefficient G played significant roles. Equivalence of D and G is well-known. This paper looks into the relationship among these three measures and the Lorenz curve to demonstrate that D and G are really generalizations of the primitive measure R.