I’ve long had an interest in developing a new way of looking at startup communities, based less on the usual government statistics (tax and crime rates, income growth and so forth) than on a cluster effect: that groups of entrepreneurs tend to attract more entrepreneurs. So, several months ago, I turned to Forbes.com contributor Darian Shirazi, founder of Radius, a San Francisco technology company that collects small business data in the U.S. and offers a marketing platform to corporate clients selling to that sector. Radius was the ideal group to generate a list of the best cities to start a business, given its ability to gather scads of information and its novel methodology for sifting the data. The result is a series of guest posts by Lisa Fugere, who manages content strategy and creation at Radius. She has put together the list of best places, along with three other posts on the cluster phenomenon, small businesses shaking up their communities and outlier regions that are mini-hotbeds of entrepreneurship…