Map shows a concentration, in purple dots, of air release, or emissions, sites across the United States. Major cities, including Los Angeles, New York, and Chicago, are labeled. Heavy concentrations of dots appear around urban centers, and the eastern half of the country appears largely in dots with little uncolored space. The western half shows a sparser distribution of dot air emissions sites, mostly centered around cities. A large amount of space with no dots appears on the western half of the map. © 2013 United States Department of the Interior

The map above shows air release, or emissions, sites across the United States. These sites include locations such as smokestacks, factories, and high vehicle traffic areas. The data in the map most directly relate to potential negative and positive externalities affecting
commons
incentives
free riders
free resources