Clustering and Modern Urban Centers

A fascinating BBC feature on the power of London –

http://www.bbc.co.uk/news/resources/idt-248d9ac7-9784-4769-936a-8d3b435857a8

Why do skilled workers cluster in key urban centers?

https://www.philadelphiafed.org/-/media/research-and-data/publications/business-review/2015/q3/brq315_big_cities_and_the_highly_educated.pdf