But people have laid out the economic advantage of mass migration all of the time. Not saying you have to agree with it but it would be untrue to claim no one has laid it out.
The broad strokes go like this:
Immigration, both skilled and unskilled, increase a nation's greatest resource - people. People produce things. Whether they're picking oranges or innovating at NASA. More people means more production. And within that increased production comes the greater probability that some of that production will accelerate your nation further ahead of others. Additionally, with falling birthrates, nation's run the risk of the not being able to provide the services to which their citizens are entitled or have earned. Immigration addresses that as well. The economic advantage of mass migration are basically cheaper labor for the production of goods and services that benefit the nation and enough people to maintain the tax base necessary to continue providing 1st world nation benefits.
Most the of arguments against are about who specifically wins and loses in the economic maelstrom. Or the false moral points about losing cultures or some other element which isn't really defined, let alone measurable.
Like I said - you don't have to agree with that argument but it has been laid out by many, many people over the last 30 years.
