Here is a book that investigates the effects of migration from third world nations to more advanced nations.

http://www.amazon.com/gp/product/0739115057?ie=UTF8&tag=wwwviolentkicom&linkCode=as2&camp=1789&creative=9325&creativeASIN=0739115057

There used to be a joke about migration from Oklahoma to Texas raising the average IQ of both states. That is just a joke. In reality, migration from Mexico to Texas lowers the average IQ of both. I think history bears that out. When I was in high school the average IQ in Texas was about 102, and there were not many Mexicans in the state. Now about 1/3 of the people in Texas are Mexicans (or from other Latin American nations) and the average IQ in Texas is 98.