The HPBIN Procedure

Quantile binning aims to assign the same number of observations to each bin, if the number of observations is evenly divisible by the number of bins. As a result, each bin should have the same number of observations, provided that there are no tied values at the boundaries of the bins. Because PROC HPBIN always assigns observations that have the same value to the same bin, quantile binning might create unbalanced bins if any variable has tied values. For more information, see the section Binning Computation and Formulas.