What is the advantage of grouping countries into five GDI groups instead of ranking them according to the absolute deviation from parity?

The female and male HDIs for many countries are approximations of the HDIs rather than highly accurate values because of the imputed wage ratios of 0.8. In order to avoid a possible wrong interpretation of the ranks based on approximate values, we grouped countries into five GDI groups by absolute deviation from gender parity in HDI values. Group 1 countries with high equality in HDI achievements between women and men: absolute deviation less than 2.5 percent; group 2 countries with medium-high equality in HDI achievements between women and men: absolute deviation between 2.5 percent and 5 percent; group 3 countries with medium equality in HDI achievements between women and men: absolute deviation between 5 percent and 7.5 percent; group 4 countries with medium-low equality in HDI achievements between women and men: absolute deviation between 7.5 percent and 10 percent; and group 5 countries with low equality in HDI achievements between women and men: absolute deviation from gender parity greater than 10 percent.