This is what happens when you have freedom of movement over a log period of time. People are going to love where the opportunities are, especially if it’s made easy. I bet a similar graph for the US would show people moving to states like CA and NY.
Yes, using fixed widths with media queries is a fairly common approach (sometimes termed adaptive web design rather than responsive web design). If you feel that the design needs more control (over proportions, etc) then it's sometimes a good trade-off but it's a decision I'd make on a project by project basis.