Ok so a huge wall. Around all our countries. While still making them work for us? Why would they accept that? Why wouldn't they just start working for themselves?
And you want to build a wall around all Europe and USA? Oo
Walls are already there, and more will be built.
"Making them work for us"... well, you see this is one of the problems. According to some researches: "An employment rate of two percent is consistent with the previous experience in Germany of immigrant integration programs, particularly from asylum seekers..." (
http://www.bild.de/geld/wirtschaft/fluechtling/nur-jeder-50te-findet-einen-job-43786808.bild.html - sorry it's in german, but on some far-right sites you can find good translations
.) So, as you can see they aren't really working for us, but they will cost approximately 55 billion EUR per million immigrants.
Most of the third world economies can't "just start working for themselves" as these economies mainly concentration on raw material production. Without a well developed processing industry (what is here, not there) they wouldn't get too far.