For some functional forms, the Gini index can be calculated explicitly. For example, if "y" follows a lognormal distribution with the standard deviation of logs equal to formula_23, then formula_24 where formula_25 is the error function ( since formula_26, where formula_27 is the cumulative standard normal distribution). In the table below, some examples for probability density functions with support on formula_28 on are shown. The Dirac delta distribution represents the case where everyone has the same wealth (or income); it implies that there are no variations at all between incomes.