I could just add that I also am not aware of any study that has advocated countries of focus as the sole criterion. Most studies I've seen say that one should focus one's efforts, and that scattering resources is problematic, but that focusing on a particular country is not sufficient, and there are many other criteria and measures that need to be taken. In our testimony, we've addressed some of those other conditions that make focusing more effective.
On May 19th, 2016. See this statement in context.