Table 1.

Definition of metro/non-metro US counties according to the population size, degree of urbanization, and proximity to a metro area - US Department of Agriculture Rural-Urban Continuum Codes (RUCC) (2023). ⁹

Code	Classification of US counties based on the definition of metro/non-metro areas
1	Metro – counties in metro areas of 1 million population or more
2	Metro – counties in metro areas of 250,000 to 1 million population
3	Metro – counties in metro areas of fewer than 250,000 population
4	Non-metro – urban population of 20,000 or more, adjacent to a metro area
5	Non-metro – urban population of 20,000 or more, not adjacent to a metro area
6	Non-metro – urban population of 5,000 to 20,000, adjacent to a metro area
7	Non-metro – urban population of 5,000 to 20,000, not adjacent to a metro area
8	Non-metro – urban population of fewer than 5,000, adjacent to a metro area
9	Non-metro – urban population of fewer than 5,000, not adjacent to a metro area