It&#x27;s a complicated topic but there were real world &quot;experiments&quot;: In 2004 in Europe:<p>&quot;By allowing anyone in the eight relatively poor new members of the EU to come and work freely, Britain, Ireland and Sweden are putting these claims to the test. All seventy-five million people in Poland, Hungary, the Czech Republic, Slovakia, Slovenia, Estonia, Latvia and Lithuania are now free to move to Britain and work. Since wages in Poland are typically only a fifth of those in Britain, Poles have a big incentive to come and work here. If opponents of immigration are right, Britain should now be deluged with East Europeans and unemployment should be soaring.... But it isn’t. In fact, only 427,000 East Europeans have so far applied to work in Britain (many of whom were already in the country illegally) – and most stay only briefly: net migration from eastern Europe was only 48,000 in 2004.5 Unemployment remains at thirty-year lows, tax receipts are up and jobs that British people no longer want to do are being filled.&quot;<p>-- Philippe Legrain