Indicator for Economic Centers

[HP Payam]

Hello BP members,

I am researching different markets to buy my first out-of-state rental property. I have certain criteria to narrow down my searches. One of my criterion is the convenience factor which has to do with the proximity to the economic centers. 

How do you suggest to quantify this factor?

For example, I gathered some people use the number of fortune 1000 companies headquarters in each city. Although this could be a useful indicator, I don't think this is a comprehensive enough as a lot of other economic attractiveness of a city is lost by using this indicator.