Defining Edge and Core Counties

The views expressed are those of the author and do not necessarily reflect the views of ASPA as an organization.

By David Hamilton
September 30, 2016

The setting of Edge Counties is the metropolitan region that was described in the previous article of this series. Although there are numerous regional models, they consist of “counties as their most basic unit,” according to Robert Lang and Arthur Nelson in the 1999 Megaregions: Planning for Global Competiveness chapter titled “Megapolitan America: Defining and Applying a New Geography.” What sets Edge Counties apart from other counties is their rapid population growth occurring on the outer edges of metropolitan areas as their name implies. These two defining characteristics create an identifiable theoretical framework for inquiry into the field of public administration. The implications will be presented in future articles but before that discussion, a concise definition of Edge Counties is required based on an acceptable calibration of rapid population growth and geographical edge.

Defining Rapid Population Growth

Before the 2010 census, the Executive Office of the President, Office of Management and Budget (OMB)circulated Bulletin 10-2 that described 366 metropolitan statistical areas (MSA) that included 1,100 of the 3,142 counties in the United States. But not all of the 1,100 MSA counties are actual functioning county governments. In preparing the criteria for the census, the OMB placed “equivalent entities,” within the overall groupings of MSA counties. Any study of county government requires close scrutiny to ensure that only functioning counties, boroughs and parishes are considered.

Defining Edge County population growth involves collecting and assembling population data over a selected period of time for all counties contained within MSAs. To present a current description, population data from the decennial U.S. Census for a period of 20 years is utilized to reflect a contemporary picture of population growth. The three distinct years of 1990, 2000 and 2010 offer three decennial census data sets based on actual population counts rather than statistical projections.

Developing the initial list of metropolitan growth counties is relatively straightforward. The mean level of growth for all counties contained within MSAs is calculated along with the rate or percentage of growth for each county within the MSAs for the 20-year period, from 1990 to 2010 using the following equation:

(2010 population – 1990 population) / 1990 population

A similar equation was used to calculate the total percentage population increase of the 1,085 MSA counties between 1990 and 2010. The standard deviation of the percentage change for all MSA counties was 30.21 percent. To establish a cutoff for the list of rapid-growth metropolitan counties, the parameters of one standard deviation or higher are set. Therefore, counties with percentage changes in population that put them in the upper two-thirds (33.0 percent and over) meet the requirements and were are considered high-velocity growth counties.

Defining the Geographical Edge

Edge or fringe are simple words with complex implications. They were used interchangeably in common practice but definition requires clarity. Edge means a sharp terminating border where something else begins while fringe denotes that which lies at the borderline. Both describe a place where something changes. But the concept of fringe—and its counterpoint core —quickly dissolve within the sprawling realities of metropolitan regions. This was why tangible criteria and adaptive terminologies are needed to determine the locational definition of the edge counties.

First, a central bearing point establishes the geographical location of each of the growth counties within the multi-county regions. Without a recognized core, the definition of edge becomes a vague subjective call, based on visual interpretation. Instead, universal criteria must be established and applied to the growth counties within the 366 MSAs. The process utilizes identifier principal cities and primary counties.

The largest cities within each metropolitan statistical area are designated as principal cities by the OMB. Up to three of them were used to create the name of each MSA ranked in order of their population’s size. These are labelled as identifier principal cities. The county that contains the most populous identifier principal city is termed a primary county and considered to be form the core of the region.

In addition, all non-growth counties located adjacent to the borders of each primary county are considered to form part of the contiguous core. For example, of the Minneapolis-St. Paul-Bloomington MSA, Hennepin County is the primary county and Ramsey County was located along its borders. As a non-growth county, it joins Hennepin County to form the core of the region.

Not all metropolitan growth counties are Edge Counties. Some of them are actually primary counties such as Hillsborough County, Florida that contains the identifier principal city of Tampa. Thus, each metropolitan growth county must be assessed to determine its regional location based on the presence or absence of identifier principal cities within them.

Although identifier principal cities provide a relatively consistent pattern within the metropolitan regions, in some instances, additional criteria are required to enhance the focus of the identifier principal city as the regional focal point. The remaining metropolitan growth counties that surround the periphery of the primary county are Edge Counties, described in the following definition:

Edge Counties are county governments that experience rapid growth over a 20-year period at levels at or above one standard deviation of all metropolitan counties. They are located at or beyond the periphery of the region’s core and are a significant contributor to the expanding populations of Metropolitan Statistical Areas. 

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Author: David Hamilton is a public administrator and change leader with experience managing county and city governments. He recently completed his DPA at Hamline University focused on the administrative impact and challenges of rapid-growth on regional governments. He currently heads his own consulting firm guiding local governments with visioning, planning and organizational alignment. David is the current president of the Suncoast Chapter of ASPA.

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