[_iyig]

I would refer you to the Putnam study from another comment, which defines homogeneity/heterogeneity in terms of ethnicity.

Certainly ethnicity is a fluid concept. The language, value system, and cultural context of a Texan may differ from that of a Minnesotan. However, I think we can agree that your average Texan or Minnesotan will likely have a greater common understanding if paired together than with your average Swiss or German person.

[lkjhdcba]

Your study is based in the States, which has a long history of segregating cultures and even language according to ethnic lines. On the other hand, I mean is that both Switzerland and Germany have a diversity of peoples, cultures and languages (e.g. Switzerland itself has 4 official languages and German has a myriad of dialects) and many citizens of these countries consider themselves pretty diverse in that regard though they are mostly white, but is that what people mean by "diversity" when they talk about "population heterogeneity"? Or is it just "diversity is when people have different skin tones and the more skin tones there are the more diverse it is"?