Have you noticed big changes to your high street / city centre / shopping malls? All the malls in my city have gone upmarket. In general the middle ground is gutted and everything is either nice looking fashion shops (even Primark looks shiny these days!) mainly for women or betting / charity / pawn shops. Even my local supermarket has a big section with dedicated cosmetics staff.

What I can't intuitively see is why there is a tendency for the middle ground to be gutted.