What's a UPG? And What About the 1%?

I had this question from one of my elementary kids last week.
Me: An unreached people group
Student: oh right.

Even as I have prayed for UPGs for several years I was always confused when a prayer guide would call a group unreached when they had 1% Christians.

The follow video explains...

The same week I saw this video God showed me the story of the Ethiopian eunuch who accepted Christ after meeting Philip on the road.  He then took the gospel back to Ethiopian and the country was the then the Christian Nations in Africa.  One man started a movement of Christianity for a whole country.  I can understand that it's less likely that one person will evangelize a whole people group, but I can't help praying for the 1% Christians among the unreached to be used to reach more.