Jesus said in Matthew 24:14 "This gospel of the kingdom shall be preached in the whole world as a testimony to all the nations, and then the end will come." Jesus directly links His return to the fulfillment of the Great Commission. While no one knows the date or time of His return, we do know that this gospel of the kingdom must be preached to all the nations first. Revelation 5:9 and 7:9-10 show that there will be some from every tribe, tongue, nation and people before the Throne.
Joshua Project is a research initiative seeking to highlight the ethnic people groups of the world with the least followers of Christ. Accurate, regularly updated ethnic people group information is critical for understanding and completing the Great Commission.
The Project gathers, integrates and shares people group information to encourage pioneer church-planting movements among every ethnic group and to facilitate effective coordination of mission agency efforts. They compile the work of numerous missions researchers to develop a list of all ethnic peoples that is as complete as possible.
For more info, see http://joshuaproject.net/joshua-project.php.