Interesting research that challenges the agglomeration argument in the UK
Research shows that the differences in productivity across the UK is modest when adjusted for factors including employment rates, commuting, industrial mix and occupational structure.
The result is that promoting growth and jobs in less prosperous parts of the UK does ‘damage’ the productivity of the country’s economy as a whole.
http://shura.shu.ac.uk/24893/1/local-productivity.pdf
Gert Kamstrup 