Foreign vs National: Who is reaching the UPGs?

Who is doing most of the pioneer missions work on the mission field today – foreign missionaries or national missionaries?  By pioneer missions work, I guess I will define it as making disciples among unreached people groups, so it is actually more specific than just planting churches where there were none previously.  

I would like to hear what you have to say on this topic, because I hear a lot of ministries say that 90% or more of pioneer missions work is being done by national (or indigenous, native, local) missionaries.  On the other hand, I have also heard that national missionaries are not doing a great job of purposefully reaching out to the remaining unreached people groups.  Instead they tend to reach only their own people and rarely become a cross-cultural missionary.  Yet, I know that many of the largest ministries that support indigenous missionaries are reporting that they are engaged in cross-cultural ministry and focusing on unreached people groups.  National missionaries also now have a numerical size advantage.  I’ve heard up to 300,000 national missionaries vs 100,000 foreign missionaries.  So who is reaching out and winning unreached people groups?  Nationals, foreigners, or a combination of both?  Or maybe you reject my question altogether and want to revise it in some way.  You can also post any sources and reading that might be relevant to this issue.  Thank you so much and God bless you.