I agree with Posner that illegal immigrants are generally productive members of the labor force, and make relatively little use of taxpayer-funded programs, such as Medicaid and other welfare programs. On the other hand, they pay little in taxes since they are frequently paid in cash and often do not pay either social security taxes or income taxes. In effect, they largely receive as take home pay what they add to the output of the country.
It is also abundantly clear that, despite the rhetoric in the Republican campaign debates, the US will never try to ship 11 million illegal immigrants back to Mexico or the other countries they came from. Some form of de facto amnesty may be inevitable for the vast majority of these immigrants. Still, I find it difficult to simply accept wholesale violation of US immigration laws, especially since, as Posner indicates, illegal immigration will pick up again as the American economy continues to recover from the Great Recession. Further immigration from Mexico is surely to be expected as long as typical young Mexican workers can increase their earnings several fold by migrating illegally to the United States.
Beyond amnesty, what can be done to discourage further illegal immigration to America, and reduce the number of illegal immigrants who are already here? Perhaps extending the wall on the Mexican-US border would help a lot, although I anticipate that would-be illegal immigrants and their “mules” would create additional crossing points into the United States where there is no wall.
A more promising approach is to tighten the enforcement of laws against employers who hire illegal immigrants.