I think it would be very interesting to add data on
number of languages per country (spoken by native speakers, both what is classified as "indigenous" and "immigrant")
number of second language speakers of English, Spanish and other major languages
number of different language families per country
number of endangered languages per country
language of school system
These indicators are interesting because they interact with colonialism, climate, poverty, economic growth and globalisation.
This information can be easily retrieved from online public databases such as the Ethnologue, Glottolog and UNESCOs Atlas of the Worlds Languages in Danger. I am a linguist and I can help out with this. I like Gapminder a lot and I'd be more than happy to contribute.
As a diversity linguist I am of course interested in what are the historical reasons for diversity to occur and what is happening in the world now. Needless to say, the loss of linguistic and cultural diversity is a loss to all of us on this planet. Two of the most harmful myths that contribute to this is are that a) some languages are better than others and b) multilingualism is bad. I stress this because two of the drivers of language extinction are economic growth and colonialism and this, in addition to the two myths just mentioned, leads to misunderstandings that language endangerment is not a problem.
Sorry, I realise I need not go into this right now. Please do contact me if you have comments our questions.
Here is an interesting publication on the correlation between language endangerment and economic growth
Tatsuya Amano, Brody Sandel, Heidi Eager, Edouard Bulteau, Jens-Christian Svenning, Bo Dalsgaard, Carsten Rahbek, Richard G. Davies, and William J. Sutherland. Global distribution and drivers of language extinction risk. Proc R Soc B, 2014 281:20141574 DOI: 10.1098/rspb.2014.1574
The article can be found here: http://rspb.royalsocietypublishing.or...
p.s. jag är svensk, om ni vill kan vi kommunicera på svenska också/istället.