Countries each having the same HDI gap [OC]

Each of these countries have the same gap in human development (0.056), with errors at most 0.002 higher or lower, these are the exact countries that are the closest to the gap in HDI.

What really fascinates me is that Ghana, Togo, Benin and Burkina Faso are all literally right next to each other and have about the same gap of human development as Türkiye to China or China to South Africa. Such a coincidence.

Sources used: https://hdr.undp.org/data-center/human-development-index#/indicies/HDI

Tool used: https://nces.ed.gov/nceskids/graphing/classic/index.asp

PS I am not really good at creating graphs so this is the best I can do.