The Migration Policy Institute estimates that the total stock of illegal immigrants in the United States has fallen slightly, from 12.1 to 11.9 million, between July 2008 and July 2009, due to the poor economy. (Inflows of legal migrants continue.) What’s interesting is that those numbers haven’t fallen more. The Economist argues that even in a recession, there are substantial economic gains to be had by remaining in the country. I wonder as well whether the political uncertainty surrounding immigration enforcement and the possibility of much stricter border enforcement in the future are keeping immigrants here because they fear having to try to get back over the border once the economy improves. The Economist story above also reports on a study showing the economic benefits that migrants bring back to their homelands when they return, benefits that are presumably now being foregone. So someone explain to me again: why can’t we get a broad-based guest worker program set up?