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Data & Tools

Introduction to Data and Tools
How do we define a "city?"
Top Data Sources: A to Z (ACS to Zillow)

Introduction to Data and Tools

At City Observatory, we’re obsessed with data:  we aim to use data to quantify every aspect of cities and city living, from their economic performance, to urban form, to walkability, to weirdness.  We actually did write the book on using socioeconomic data to better understand local economies:  you can find it here.  One of our key objectives is to make this data widely available to a range of audiences.  Visit this section of our website to learn more about where to find the most compelling, data-driven insights about cities.

How do we define a "city?"

What’s a city?  It’s almost too fundamental a question to ask, but what do we mean when we say “city?”  The term is used in different contexts to mean different things, and if we’re to make sense of many of the claims and counterclaims about what cities are, and how they are performing, it helps to have specific definitions.

The city as metropolis:  Sometimes we define city to be the urban half of the “urban/rural” dichotomy:  as in town and country.

The city as municipality:  Sometimes we use city in a narrow legal sense:  the “city of New York” a municipal corporation with precise boundaries set by law, governed by an elected Mayor, Council and other officials.

The city as downtown:  Sometimes we mean city as the dense urban core of a metropolitan area; its downtown and nearby environs, “the city center.”

Sometimes we mean city as that generally more “urban” area with higher residential densities as juxtaposed to “suburbs”—lower density development more peripheral to the metropolitan area.

These three varying uses of the term city—city as metropolis, city as municipality, city as downtown—have distinctly different statistical definitions.

The city as metropolis corresponds to metropolitan statistical areas—units defined by the federal government as groups of counties that share an urban population center and represent a common labor market, as inferred from journey to work patterns.  Metropolitan areas are defined intentionally to be roughly comparable to one another.

The city as municipality is defined by the political boundaries of the largest (or occasionally two largest) municipalities in a metropolitan area.  City boundaries vary widely from place-to-place due to historical accident and variations in annexation laws.  Some municipalities (Phoenix, Jacksonville, San Antonio) account for a majority of the population in their metropolitan area (and encompass areas that would be regarded as “suburban” in most regions.  Other municipalities encompass fewer than one in six metropolis residents.

The city as downtown or urban core is defined by density, geography and function.  Urban cores—the area including the central business district and immediately surrounding neighborhoods, is usually the oldest, densest part of most metropolitan areas, and is the center of important civic, cultural and commercial functions.  The exact boundaries of downtowns are difficult to define.  One rough approximation for the urban core is the three-mile radius around the center of the central business district, a measure popularized by Ed Glaeser and his colleagues

To get a sense of the varying geography of city centers, municipal boundaries and metropolitan areas, you can view our map of these boundaries for each of the nation’s largest metropolitan areas here.