In business literature there is a well-known effect called "the Matthew effect"; it especially impacts viral startups. The rule is taken from the parable of the servants: he who is profitable in little things will get even more. In secular terms it translates to "the rich get richer and the poor get poorer." It's also known as Accumulated Advantage. Unfortunately we see this effect in missions, too. Whenever agencies, churches or denominations decide to send teams on one of two factors:
... the Accumulated advantage effect can set in.
If we, for example, send teams to where there are strong teams, then the strongest teams tend to attract more teams, and weaker teams get less or nothing. Eventually all of our teams will clump in certain areas and places outside will have no access. This is in fact what is happening now.
If we send to where there is response, we tend to build on existing efforts. More effort yields more response. We don't hear about response elsewhere and make the mistake of thinking other places are therefore unresponsive. This reinforces the cycle: go where the wind is blowing.
This is a critical mistake that in part has driven us to where we are now and exacerbated the problem. Even in work among the Unreached, a lot of workers are clumped into specific areas. If we only go to the places where teams are strong and things are popping we never send teams to those who have no access.
We don't know if they might be responsive if we never go and find out. Are the Luri, Qashqai, Saudis, Uzbeks, etc truly unresponsive--or have they never had a chance?
This is an "Evil Matthew effect," so to speak.
We need people like Philip (who went as the Spirit drove him), Peter (in response to the dream), Paul (Macedonian call), probably others like Thomas (Church history says India)... if we are only going to where there are existing teams how can we follow Paul's model: "It has always been my ambition to preach the gospel where Christ was not known, so that I would not be building on someone else's foundation."
If we are going to see the task completed, we have to break out of where our existing teams are, and brave the risk to go beyond.