"For evangelization purposes, a people group is the largest group within which the Gospel can spread as a church planting movement without encountering barriers of understanding or acceptance" (Source: 1982 Lausanne Committee Chicago meeting.)
In most parts of the world, lack of understandability acts as the main barrier and it is appropriate to define a people group primarily by language, with the possibility of sub‐divisions based on dialect or cultural variations. Such a list may be referred to as an ethno‐linguistic list of peoples.
In other parts of the world, most notably in portions of South Asia, acceptance is a greater barrier than understandability. In these regions, caste, religious tradition, location, and common histories and legends may be used to identify the primary boundary of each people group. Language can be a secondary boundary.
What distinguishes one people group from another?
Ideally, "people group" would always be defined to mean (a) all individuals in the group who understand each other reasonably well and (b) cultural / relationship barriers aren't so high that the transmission of the Gospel is seriously impeded.” (Joshua Project)
Even if these numbers were slightly off, I think we can agree that there is much work to be done. It is our passion to equip the indigenous Christians to have the eyes of their heart enlightened with God’s eternal plan for reaching these UPGs. The question is not whether it is possible to reach them, the question is; what can I do to help the Church reach them. Take these facts and begin with prayer, asking God what he wants you to do.