Appendix A - 22 Rules for Selecting Counties
Rule 1
Each selected county will represent one of six size standards.
If the Black population of the U.S. is classified into (roughly) six equal groups based on the size of the Black population where they live, the following breakdown emerges (please note that all population figures in this section refer to the Black population, not total population):
- 15.9 percent (5.5 million) live in just six major metropolitan counties: Cook County, IL (Chicago), Los Angeles County, CA, Kings County, NY (New York City), Wayne County, MI (Detroit), Harris County, TX (Houston), and Philadelphia County, PA. The Black populations range from 1.4 million in Cook County, IL to 620,000 in Philadelphia County.
- 16.7 percent (5.8 million) live in the next fifteen largest counties (ranked by Black population). These include four additional counties in the New York City area, three counties in the Baltimore-D.C. area, two each in the Atlanta and Miami areas, and four independent counties corresponding to the core counties of Dallas, Memphis, Cleveland, and New Orleans. The largest of these counties has 505,000 Black residents and the smallest has 277,000.
- 17.2 percent (6.0 million) live in the next group of 39 metropolitan-area counties across the country. The largest of these counties is Alameda County, CA (Oakland), with 268,000 Black residents, and the smallest is Guilford County, NC (Greensboro) with 104,000 Black residents. Examples of other counties in this category include Richmond, VA, Charleston County, SC, Jefferson, KY (Louisville), Erie, NY (Buffalo), and Jackson, MO (Kansas City).
- 16.7 percent (5.8 million) live in the fourth-largest group of 79 small urban and suburban counties. The largest of these is Caddo Parish, LA (Shreveport), which has 103,000 Black residents, and the smallest is Lafayette Parish, LA (approximately 20 miles west of Baton Rouge), which has 46,423 Black residents. Examples of other counties in this category include Montgomery, PA (Philadelphia metro), Orange, CA (Anaheim and Santa Ana), Spartanburg, SC (in the northern part of the State), Pierce, WA (Tacoma), Monmouth, NJ (in the central part of the State), and
Chesapeake, VA.
- 16.7 percent (5.8 million) live in 227 "small city" counties. The largest of these is Galveston County, TX, with 46,407 Black residents and the smallest is Mississippi County, AR (20 miles north of Memphis, TN) with 15,326 Black residents. Other examples in this category include Dane, WI (Madison), Colleton, SC (a suburb of Charleston), Ascension Parish, LA (southeast of Baton Rouge), Glynn County, GA (on the Atlantic coast), Craven, NC (also on the Atlantic coast), Gloucester, NJ (a suburban county of Philadelphia), and Stark, OH (Canton).
- 16.7 percent (5.8 million) live in the other 2,800 counties throughout the U.S. About 1,000 of these counties have fewer than 100 Black residents, and 153 counties have Black populations of more than 10,000 but less than 15,300. The largest of these counties is Copiah County, MS (south of Jackson), which has 15,274 Black residents. Other examples of counties with more than 10,000 Black residents include Chester, SC, Walton, GA, Lafourche Parish, LA, Meriwether, GA, Liberty, TX, and Kaufman, TX. These counties are typically not associated with metropolitan areas, but are classic "small-town America."
Exhibit A-1
Six U.S. Black Population Groups by Community Size
 d
Rule 1 therefore required that one selected site fall into each of the above size categories.
Rule 2
The six counties will, in combination, reflect the geographic distribution of the Black population across the U.S.
A regional approach was used to maximize flexibility. The U.S. Bureau of the Census defines U.S. regions as follows:
- Northeast Region: CT, MA, ME, NH, NJ, NY, PA, RI, and VT.
- South Region: AL, AR, DC, DE, FL, GA, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, and WV.
- Midwest: IL, IN, IA, KS, MI, MN, MO, NE, ND, OH, SD, and WI.
- West: AK, AZ, CA, CO, HI, ID, MT, NV, NM, OR, UT, WA, and WY.
The Black populations of each region are:
Exhibit A-2
U.S. Black Population by Region
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Region
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Black Population
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% of Total
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Northeast
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6,371,000
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18.3%
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Midwest
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6,409,000
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South
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18,679,000
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West
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3,377,000
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Total
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34,836,000
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Based on these data, an initial rule was defined to require that three of the six study sites be located in the south, and one each be located in the other three regions. In light of other factors, the rule was later relaxed so that a community in the western region was not required.
Rule 3
Rules 1 and 2 were combined to optimize the combinations of community size and region.
A review of the Black population by region and by community size revealed some strong patterns. For example, the South region contains 84 percent of the communities in the smallest-size category, but only one of the six communities in the largest-size category. The study team conducted a small optimization process, and determined the combination of community size and regions that should be selected in order to maximize population coverage.
Exhibit A-3 shows the Black population by community size and region. The optimized selection process produced rules that one site should fall into each of the six size/geography categories. Note that the categories selected also ensure compliance with Rules 1 and 2. (The rule requiring a western site was later relaxed.)
Exhibit A-3
Black Population by Size and Region
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Population Category
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Northeast
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South
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Midwest
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West
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Grand Total
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1,550,000
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645,000
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2,295,000
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1,044,686
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5,535,000
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275,000-599,999
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1,704,000
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3,750,000
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376,000
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0
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5,831,000
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104,000-274,999
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735,000
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2,756,000
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1,546,000
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960,000
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5,997,000
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46,420-103,999
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1,392,000
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3,119,000
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663,000
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657,000
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5,830,000
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15,300-46,419
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596,000
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4,017,000
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808,000
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410,000
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5,830,000
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Less than 15,300
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394,000
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4,391,000
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722,000
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307,000
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5,813,000
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Total
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6,371,000
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18,679,000
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6,409,000
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3,377,000
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34,836,000
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Rule 4
At least one site will be located within two hours' driving distance of Washington, DC.
This rule was defined to enable NHTSA headquarters staff to cost-effectively monitor the focus group process in at least
one community.
Rule 5
The Black population of a selected county must be at least 10,000.
This rule was put in place for practical purposes to ensure an adequate population pool from which to conduct focus groups. While this rule eliminated more than 80 percent of U.S. counties from consideration, it only eliminated about 11 percent of the Black population from consideration.
Rule 6 through 22
For each of the seventeen remaining data measures, the six sites shall represent a continuum of the data range across the U.S.
For each of the seventeen remaining data measures, all U.S. counties were grouped into six separate and unique categories that reflect the data. For example, the data measure regarding employment growth included six categories that ranged from rapid growth to very slow growth, while the data measure regarding the Black proportion of the population included six measures ranging from communities with large proportions of Black residents to communities with low proportions of Black residents.
A decision rule was set up as follows for each data measure: the six selected study sites should each fall into a different category for that specific data measure.
Category definition for each data measure was an important part of this process. Counties were placed in one of six categories for each data measure via the following process.
- The 3,141 counties in the U.S. were ranked from 1 to 3,141 according to their value for the particular data measure (for example, one of the data measures was the proportion of the local population that is Black, so the study team ranked all U.S. counties from the highest proportion of Black people in the population to lowest proportion of Black people in
the population).
- The Black population figure was obtained for each county.
- Beginning at the top of the list, the study team added up the Black population of the highest-ranked counties, working down from the top-ranked county, until one-sixth of the U.S. Black population (approximately 5.8 million people) was accounted for. These counties at the top of the list were arbitrarily termed "top tier" counties and comprised one category.
Example
Developing Categories for the Data Measure
"Percent of Population that is Black"
Macon County, Alabama, has the highest proportion of Black people in the nation at 86.7 percent, and Jefferson County, Mississippi, is second with 86.6 percent. Macon County's 19,937 Black people were summed with Jefferson County's 7,260 Black people, which were summed with the third-ranked county's Black population, and so on until 5.8 million Black people were included. This occurred after 172 counties were summed, ending with Thomas County, Georgia (43.5 percent Black).
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- Beginning where the "top tier" counties ended on the list and continuing down the list, the study team added up the Black population until another one-sixth of the U.S. Black population was accounted for. The counties in this second tier (termed "well above average") comprised the second of the six categories.
Example (continued)
The county ranked below Thomas County, Georgia, was Greene County, North Carolina, where the Black population is 43.4 percent of the total population. Greene County's 8,052 Black people were summed with the 97,916 Black people in Georgia's Chatham County (also 43.4 percent Black), and so on, until 5.8 million Black people were included (one-sixth of the U.S. Black population). This occurred after 176 counties were summed, ending with Bulloch County, Georgia (31.4 percent Black).
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- Beginning where the "well above average" counties ended on the list, the study team began adding up the Black population of the next-ranked counties, moving down the rankings until yet another one-sixth of the U.S. Black population was accounted for. This new group, termed "above average" comprised the third category.
Example (continued)
The county ranked below Bulloch County, Georgia, was Tangipahoa Parish, Louisiana, where the Black population is 31.4 percent of the total population. Tangipahoa Parish's 30,885 Black people were summed with the 63,547 Black people in Virginia's Chesapeake City (31.3 percent Black), and so on, until 5.8 million Black people were included. This occurred after 141 counties were summed, ending with Chatham County, North Carolina (23.4 percent Black).
Note that LA has parishes instead of counties, and VA has both counties and independent cities that function as combined city/county governments.
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- Beginning where the "above average" counties ended on the list, the study team continued adding up the Black population until another one-sixth of the U.S. Black population was accounted for. This new group, termed "below average" comprised the fourth category.
Example (continued)
The county ranked below Chatham County, North Carolina, was Hamilton County, Ohio, where the Black population is 23.4 percent of the total population. Hamilton County's 196,403 Black people were summed with the 4,106 Black people in Virginia's King George County (23.2 percent Black), and so on, until another 5.8 million Black people were included. This occurred after 131 counties were summed, ending with Lawrence County, Alabama (17.0 percent Black).
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- Beginning where the "below average" counties ended on the list, the study team continued adding up the Black population until another one-sixth of the U.S. Black population was accounted for. This new group, termed "well below average" comprised the fifth category.
Example (continued)
The county ranked below Lawrence County, Alabama, was Mahoning County, Ohio, where the Black population is 17.0 percent of the total population. Mahoning County's 42,912 Black people were summed with the 3,814 Black people in Texas's San Jacinto County (16.9 percent Black), and so on, until another 5.8 million Black people were included. This occurred after 200 counties were summed, ending with Seminole County, Florida (10.2 percent Black).
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- Beginning where the "well below average" counties ended on the list, the study team grouped all remaining counties into the sixth and final category, termed "bottom tier." According to the calculations in the previous steps, this category by default contained the final one-sixth of the U.S. Black population.
Example (continued)
The county ranked below Seminole County, Florida, was Indian River County, Florida, where the Black population is 10.2 percent of the total population. Indian River County's 42,912 Black people were summed with the 3,176 Black people in Texas's Hill County (10.2 percent Black), and so on, down to the county ranked 3,141st, which in sum included 5.8 million Black people. A total of 2,321 counties were included in this category. (1,013 counties have no estimated Black population, and thus a total proportion of zero percent.)
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- The net result is that the Black population is divided into six equal population segments for each data measure. For the example shown, the following graph shows six segments of approximately equal size, one with high proportions of Black population, one with low proportions, and others at various gradations in between. One of the seventeen rules thus states that each of the six selected sites will fall into a separate category for this measure, ensuring a mix of communities in terms of the prevalence of the Black population in the community.
Exhibit A-4
Black Proportion of Population - Category Definition
 d
This same process was used to categorize counties for each of the sixteen other data measures, and rules were set up to ensure a variety of communities for each of those other measures. One other example is shown below, in terms of local employment growth rates.
Exhibit A-5
Ten Year Local Employment Growth Rate - Category Definition
 d
Note that a particular county will not always fall in the same tier for different data measures. For example, Macon County, Alabama is in the top tier in terms of the proportion of the population that is Black, but is in the bottom tier in terms of employment growth. Also, the terms "top tier" and "bottom tier" are arbitrary in terms of the model development; no judgments are necessary as to one end of the spectrum being more desirable for a community than the other end.
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