Based on what's shown in the other graph, there are a few cities that are extreme outliers (such as Stone Mountain and Clarkston). Doing an average on such data

Based on what's shown in the other graph, there are a few cities that are extreme outliers (such as Stone Mountain and Clarkston). Doing an average on such data won't show a trend so much as it will reflect on how much these outliers sway the average. It's like proving that everybody got rich in a town overnight since the average income shot up while Bill Gates came for a visit.