Comparison of population structure between studies can be difficult, because the value of the often-used F_ST-statistic depends on the amount of genetic variation within populations. Recently, a standardized measure of genetic differentiation was developed based on G_ST, which addressed this problem, though no method was provided to estimate this standardized measure without bias. Here I present a method to estimate a standardized measure of population differentiation based on the analysis of molecular variance framework. One advantage of the method is that it can be readily expanded to include different hierarchical levels in the tested population structure.