[Air-L] Twitter users by country?

Hey all, I'm looking for a relatively recent (2014 or later) dataset that robustly estimates Twitter users by country* to contextualize other variables. If you know of such a dataset -- or of a researcher likely to know -- could you please contact me? Many thanks! Amy *I'm looking for as close to ALL countries as I can get, not the ends of the spectrum. --- @shrapnelofme