Since June 2003, the Census Bureau has tracked “micropolitan” statistical areas—areas identified as having an urban cluster of between 10,000 and 49,999 population, along with the traditional metropolitan areas—areas with an urban core of at least 50,000 residents. Together, metropolitan and micropolitan areas are known as “core-based statistical areas” (CBSAs). Counties not linked to urban clusters are termed “outside core-based statistical areas.”