Assuming your figures are accepted (given there is no effective measure to count in and out, therefore the figures must be to an extent guess work) the population of Cambridge is about 123000. That's 40000 fewer than the increase you cite. It therefore follows that the increases you mention would require a town/city the size of Cambridge to be built every single year, where do you suppose they are built? Do try to remove all your inverted snobbery, and just look at no more than the numbers of people in conjunction with the simple question, where do they go?