Stephane Tajick Consulting created the Economic Power Ranking of world cities as a part of its Global Residence Index. The Index rank all the world cities based of where the wealth and economic top performers reside. Strongly based on Forbes Billionaire List and Top 2000 Largest Public companies, the Index rank the top 500 world cities. Cities were judged on there area of influence, meaning cities like San Francisco incorporated other towns like Silicon Valley and San Jose to form the San Francisco Bay Area.
Here is a quick look at the top 10:
The full list with number of billionaires and top companies is visible here The STC Economic Power Index