The April 6 issue of New Scientist has a special focus on immigration. All worth a read, but here's an assessment of the horrible cost:
"A meta-analysis of several independent mathematical models suggests it would increase world GDP by between 50 and 150 per cent. “There appear to be trillion-dollar bills on the sidewalk” if we lift restrictions on emigration, says Michael Clemens at the Center for Global Development, a think tank in Washington DC, who did the research."
And the uncontrollable hordes:
"Niger is next to Nigeria, Nigeria is six times richer and there are no border controls, but Niger is not depopulated. Sweden is six times richer than Romania, the EU permits free movement, but Romania is not depopulated."
Time for open immigration?