If immigrants just took advantage of the social and material benefits that their host countries provided, there would be no cultural evolution. But immigrants, and their descendants, adopt some of the ideas and institutions that make their new homes better places to live and raise families. This integration promotes the spread of ideas and institutions that encourage order, justice and economic efficiency.
These examples support the idea that societies that attract immigrants tend to have ideas and institutions that cause them to be richer, less violent and less exploitative than the societies that supply them.
As long as they vote with their feet and hearts, immigrants are a more powerful engine for social change than armies.
А то все, за колбасой-за колбасой. Именно что, миграция и должна осуществляться по градиенту колбасы :)