At a recent discussion forum around the definition of the unreached, I was reminded of some of the complexities and nuances involved.
The term unreached has a long history (read a great review article in the latest issue of IJFM). Concisely: "An unreached or least-reached people is a people group among which there is no indigenous community of believing Christians with adequate numbers and resources to evangelize this people group without outside assistance" (Joshua Project).
To know whether a people group is unreached requires us to ask five questions, some of which are easy and some of which are less so:
Is there a church among the people? On the surface, this is easy to answer. Part of the issue becomes what expressions of Christianity we count.
Is the church an indigenous expression? This is far harder. It can be explore through the data in the World Christian Encyclopedia and other sources. It is made complex by the fact that every country has multiple denominations or groups of churches. Each of these can be "more or less" an indigenous expression, and may span multiple people groups.
Might it evangelize this people group? This is one of the hardest questions to answer; in many cases there will be no answer that everyone (or even most) agree on. I generally interpret this to mean "all of the people group." The "might" question is exceptionally difficult to answer because it's qualitative. How do we judge whether a church might be able to evangelize a group? Is it a size question, or the type of strategy it uses, or the type of worship forms, or... This is the question that we grapple with.
Is it working on evangelizing the people group? This is far easier to answer. Plans and strategies will generally be visible. I think it's easier to look for those who "are working on" instead of those who "might be able to."
Is it evangelizing all? In some instances, church communities are already in a position to reach everybody, and are mostly doing this. In which case, the question is answered.
The challenging, "gray" zone is when a people group has a church (or multiple churches) that are indigenous expressions, and which outsiders believe might evangelize the group but they clearly are not engaged in doing so. Is the group then unreached? The operating definition of "unreached" is "has a church that can do it." If the local church can do it, it needs revival.
But this is not to say there isn't a role for outsiders. Sometimes, expats need to go where locals will not, because time is ticking away.