I used to think free and totally open borders would be ok - but life experience has changed that viewpoint- imo there is a limit to how many immigrants can be absorbed without creating social and perhaps economic problems. The fundamental problem is that over time and history people form into groups and adopt cultural practices and norms that work for them, but immigrants bring different beliefs and practices and that can lead to conflict. In the English speaking Anglo colony - pioneer cultures of Canada, US, New Zealand, Australia we originally mostly restricted entry to European races, with the exception of the US importing black slaves to work for the plantations. In more recent times immigration in NZ and other Anglo former colonies more people from Asia and in New Zealands case The Pacific Islands have been immigrating because they are wanting a better economic life and the freedoms we have. Politicians have allowed and even encouraged these immigrants from other cultures because they will work for lower wages and conditions than existing citizens will accept. Its good for the GDP in the short term. In school in the 1970s we were taught the 'melting pot' theory of racial and cultural integration- where over time divergent cultures are supposed to gradually merge into some harmonious ideal. This might work up to a point but surely has its limits and takes a long time and risks considerable internal tensions and conflict if pushed beyond those limits. Free markets are a great ideal, but human nature sometimes makes their universal application counter productive.