Melvin is right and so is Gavin. Both terms are used but each within it's own context, however as the context is within a directed argument the implication becomes confused between the two.
That said, it is therefore disingenuous to link a research into regional population variations with a pressure group's claim of the effect of immigration. Indeed, it could be inflamatory to do so where it not done so in such level terms.
However, the proposition you are making Gavin is at odds with the opposite proposition you released as a press release to the local media on calling for inward migration to support underpopulated schools. Political gamesmanship or inconsistant positioning?