Geographic Hierarchies
Zip code information has a natural hierarchy: zip codes are in counties, and counties are in states, for instance. Such hierarchies are important for understanding and effectively using geographic information. This section discusses comparisons at different levels of geographic hierarchies.
Wealthiest Zip Code in a State?
Wealth is spread unevenly across the United States. Relative wealth is often more important than absolute wealth, although actual income levels may differ considerably. This inspires a question: What is the wealthiest zip code in each state?
This question is about geographic hierarchies. Locations are simultaneously in multiple geographic areas, so zip codes are in counties and counties are in states. Someone residing in zip code 10011 in Manhattan is also living in New York County, and in New York City, and in New York State, and in the United States. Of course, a handful of zip codes straddle state and county borders, as explained in Chapter...