As we all know, in Galciv 2 their is a galactic tourism which adds to your money. Because it is now apparent that people can get around should there be imagration between civs? This would add to your population. I belive there is something in the manual about this but I think imagration should take a more active role in the game, like when there is war between two civs and refugees from both go fleeing to your civ for shelter. Also thier should be a options were you can shoose how open your borders are. This is how I would do it.

                                  Closed Borders, Example: south korea, no foreginers allowed

                                  Restricted borders, Example: soviet union, people are allowed in, but only for good raeasons like for big business.

                                  controlled borders, example: Nazi Germany, people are allowed in but they have to assimulate into the Civs own culture.

                                  Loose borders, Example: Spain, people are allowed in and civ does not aid or hurt the immagrents, some organizations do help though.

                                  Open borders, Example: U.S.A, Immagrents come in by the millions and are given the full beniftits that Civ has to offer.