American City Business Journals this week offers an in-depth look at small business in America. Our coverage includes an unveiling of our exclusive Small Business Vitality report: A ranking of 106 cities nationwide based on each city’s ability to foster the creation and development of small businesses. Ahead of Thursday’s unveiling of that ranking, we’re taking a look at some of the variables that played into the 15-part Small Business Vitality formula. On Monday, we looked at look concentration…