Abstract ：
We consider two possible cases of illegal immigrants to a developed country based on their expected lifetime income: high-risk entrance with low-risk of detection during their stay (type F migration) and low-risk entrance with high risk of detection (type S migration). We find that if medium productivity workers migrate illegally as type S immigrants, and if lower productivity workers migrate illegally as type F, internal investigation policies for type S immigrants will contribute to enhance the average productivity of illegal immigrants. On the other hand, if medium productivity workers migrate illegally as type F while lower productivity workers migrate illegally as type S, border control policies for type F immigrants will contribute to enhance the average productivity of illegal immigrants. Moreover, we find that the expansion of legal immigration (legalization of high productivity illegal immigrants) by the host country reduces the total number of illegal immigrants and enhances the average productivity of total immigrants in the two cases that were examined in this paper.

Keywords : illegal immigration, border control, internal investigation

JEL code: F22, J61