Although the brain gain in metropolitan areas will strengthen the economic benefits of agglomeration, it is hard to see how this benefits the regions from which the talented have come without redistributive policies.

ECONOMIST: Letters

These countries, the authors contend, are historical centres of economic hustle and bustle that can take advantage of agglomeration.

ECONOMIST: Economics focus

It turns out it's all about what economists call "agglomeration" - linking businesses and others kinds of economic activity together in such a way that they can start to punch above their weight.

BBC: Should Britain let go of London?