[Arragonis]

True, however two things spring to mind on this (I have no evidence to hand though...)

- The numbers of newcomers as a proportion of the size of the population already there is not significant enough to make a hige difference. It may in some areas where newcomers seek out established communities of their own origin, but not nationally - You wouldn't be able to blame immigration into the country specifically for a town expanding for example. Poeple do move around the US more than in Europe.

- Immigrants tend to absorb a lot of the culture of the country they move to - e.g. Asian (for us that is Indian sub-continent not just Oriental) families have adopted the 1-2 kids approach or having kids later once they are established for the most part at least after 1/2 generations - at least that is my experience from my in-law family (Mrs A is of Indian origin).