How is the number of groups and colours decided for partial grouping of countries?

The decision was to group countries to a small number of groups, say three, according to the values of an indicator achieved by countries. Countries are divided into three groups of approximately equal sizes (terciles): the top third, the middle third and the bottom third. A distinct shade of a selected colour is attached to a group of countries with a similar level of performance. The colour-coding scale graduates from darkest to lightest.

The darker shade represents the top third group; the moderate shade represents the middle third; and the lightest shade represents the bottom third of countries. Partial grouping of countries applies to all indicators listed in five dashboards. Sex ratio at birth of Dashboard 2 is an exception—countries are divided into two groups: the natural group (countries with a value between 1.04-1.07, inclusive), which uses darker shading, and the gender-biased group (all other countries), which uses lighter shading. See Technical note 6 at http://hdr.undp.org/sites/default/files/hdr2020_technical_notes.pdf for details.