This information is provided by Todd Gardner Population Distribution Branch, U.S. Census Bureau: The standards for defining CBSAs are given in the Dec. 27, 2000, Federal Register Notice, available on the Census Bureau's website at http://www.census.gov/population/www/estimates/masrp.html. To determine if a county qualifies as an outlying county in a CBSA the following test is employed: Section 3. Outlying Counties A county qualifies as an outlying county of a CBSA if it meets the following commuting requirements: (a) at least 25 percent of the employed residents of the county work in the central county or counties of the CBSA; or (b) at least 25 percent of the employment in the county is accounted for by workers who reside in the central county or counties of the CBSA. A county may appear in only one CBSA. If a county qualifies as a central county of one CBSA and as outlying in another, it falls within the CBSA in which it is a central county. A county that qualifies as outlying to multiple CBSAs falls within the CBSA with which it has the strongest commuting tie, as measured by either (a) or (b) above. The counties included in a CBSA must be contiguous; if a county is not contiguous with other counties in the CBSA, it will not fall within the CBSA. The numbers used in this test come from the 2000 County-to-County Worker Flow Files, available on the Census Bureau's website at http://www.census.gov/population/www/cen2000/commuting.html. The number of employed residents is calculated by adding up all counts of individuals in the 2000 County-to-County Worker Flow Files where the county in question is listed as the county of residence. Similarly, county employment is calculated by adding up all counts in the 2000 County-to-County Worker Flow Files where the county in question is listed as the place of work. If you have any further questions you can contact me at 301-763-2459. --Todd Gardner Population Distribution Branch