"The focus of the Christian missions community 200 years ago was
for the coast lands of the world.
A century later, the success of the coast lands effort motivated a new generation
to reach the interior regions of the continents.
Within the past several decades, the success of the inland thrust has led
to a major focus on people groups.
Today, followers of Christ are concentrating their efforts on the
unreached peoples of the world..
most of which are in the 10/40 Window."
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From Joshua Project.