How many people live in Sacramento County and, of them, how many live in Arden Arcade? According to the US Census Bureau, and as reported by Sacramento County, there were 1,445,806 living in Sacramento County in 2013.  881,149 people live in 7 cities in the County. 564,657 people live in the unincorporated area (the "Uncity"). That means 39% of the population of Sacramento County lives in the UnCity, which is a very high figure for California's heavily urbanized counties. If you look at the photo below you will see Santa Clara County's display at the state capitol building. Santa Clara County has 1,857,621 people, with just 5% of its population in their UnCity. 

The Census Bureau said Arden Arcade's population was 92,186 in 2010. If Arden Arcade was a city it would be the County's 3rd largest city (Sacramento and Elk Grove are #1 and #2, respectively). Sacramento County's UnCity has more people than Stanislaus County, which is the 16th largest county of California's 58 counties. Arden Arcade has almost as many people as Hesperia--a city in San Bernardino that is California's 81st largest city out of 482 cities.  If Arden Arcade was a county it would have more residents than 21 of California's 58 counties have. But since Arden Arcade isn't a city; it's just 16% of the vast UnCity of Sacramento County.