There is now an easy on-line way to document the diasporas of specific people groups.  See the article “Tracking Diaspora On Unreached Peoples Now Possible” at: www.etnopedia.info/?p=621

See a real example utilizing this tracking capability for a people group of about 40,000 from Mexico: http://diaspora.etnopedia.org/wiki/index.php/Triqui,_Copala