2006 proposed fee schedule - American Society of Clinical Oncology

(2) Metropolitan Divisions
Under OMB’s new CBSA designations, a Metropolitan
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Division is a county or group of counties within a CBSA that
contains a core population of at least 2.5 million,
representing an employment center, plus adjacent counties
associated with the main county or counties through
commuting ties. A county qualifies as a main county if 65
percent or more of its employed residents work within the
county, and the ratio of the number of jobs located in the
county to the number of employed residents is at least 75
percent. A county qualifies as a secondary county if at
least 50 percent, but less than 65 percent, of its employed
residents work within the county, and the ratio of the
number of jobs located in the county to the number of
employed residents is at least 75 percent. After all the
main and secondary counties are identified and grouped, each
additional county that already has qualified for inclusion
in the MSA falls within the Metropolitan Division associated
with the main or secondary county or counties with which the
county at issue has the highest employment interchange
measure. Counties in a Metropolitan Division must be
contiguous (See the December 27, 2000 Federal Register,
Standards for Defining Metropolitan and Micropolitan
Statistical Areas, (65 FR 82236)).