A man offers you free envelopes, as many as you want to take.
Half the envelopes contain no money. Half of the other envelopes contain a one dollar bill. Half of the remaining contains a five dollar bill. The rest a ten dollar bill.
Some envelopes actually contain debt that you must pay.
Immigrants might create social pressure until they're fully integrated, some don't know the language, and some are more likely to commit crimes or cost the state money upon deportation procedures. In Switzerland, almost three out of four detainees nationwide are foreigners (citation: http://www.swissinfo.ch/eng/swiss_news/Experts_reflect_on_sp... ).
I do think you can mitigate this by making people pull their own fees when the visa is granted, not only all the cost of the actual administrative procedures but also a median insurance fee for future detention and deportation costs broken down via a statistical model. But even then you have side-effects, like a sudden increase in San Francisco population, increased rents for housing, gentrification of neighborhoods ( http://en.wikipedia.org/wiki/Gentrification ), displacement of people that otherwise have lived their entire life in that area, and less opportunities for US nationals given the foreigner's competition.
Despite this, I still think that US should allow more immigrants, that the bar is currently set too high and that in the future we'll be able to make more progress towards the idealistic "Earth: one country one nation" slogan, but it's not as simple as taking all the envelopes.
Immigrants might create social pressure until they're fully integrated, some don't know the language, and some are more likely to commit crimes or cost the state money upon deportation procedures.
Surely that's the whole point of the immigration process, to weed out the applicants that fall into these categories... Canada and Australia both require you to prove English language ability (via IELTS test). Background check people's criminal past etc etc
I very much like Australia's immigration process, which requires independent verification of a person's skills, they have a specific skills shortage list (updated regularly) and you have to agree to respect Australia's culture and values. You want to live here then you adapt, not the other way round. I think this is the problem with too many places at the moment.
I think gentrification of neighbourhoods and displacement is happening regardless of the fact of immigration, it's the result of an aging population alongside the increase in population in general.
Half the envelopes contain no money. Half of the other envelopes contain a one dollar bill. Half of the remaining contains a five dollar bill. The rest a ten dollar bill.
Why don't you take all the envelopes?