I think the same can be argued for global investment banks. All of their important offices are in six cities globally: New York (Manhattan), London, Tokyo, Hongkong, Singapore, and Sydney. All other locations pale in comparison. Probably 1% of headcount (sales, trading, i-bankers) is responsible for 99% of revenues. There is a reason why investment banks are all crowded into very tall buildings in the same six cities: They are trying to access those "1% people". I see the same for tech clusters around the world. (For tech, I guess that less than 5% of staff generate most of your important intellectual property.) There is a reason why Oracle stays in Silicon Valley instead of moving to Montana or Oklahoma were real estate and salaries would be much cheaper!