The Atlanta metropolitan area, commonly referred to as Metro Atlanta or the Metro area in Georgia, is the ninth-largest metropolitan area in the United States and consists of 28 counties in Georgia. According to the 2000 census, the metropolitan area had a population of 4,247,981, though the 2006 Census estimate shows 5,138,223 people living in the area. Also according to the 2006 population estimates, the 28 county Atlanta metropolitan area is currently the fastest growing metropolitan area in the United States. Atlanta proper is only the 35th-largest city in the country, largely due to Atlanta's patterns of urban sprawl, and the city's inability to annex as have such cities as Charlotte, San Diego, and Phoenix. Atlanta's combined statistical area or CSA had a population in 2000 of 4,584,234. As of July 1, 2006 the CSA is estimated to be at 5,478,667.