Three of five residents of Arizona live in Maricopa County. More than 80 percent live in the Phoenix and Tucson metropolitan areas.
The annual population estimates shown in the chart are benchmarked to each of the decennial censuses. However, since the Census Bureau uses the same methodology for the entire nation, it cannot incorporate unusual situations in a specific area. For example, the passage of the “employer sanctions law” in Arizona in 2008 led to an increase in the out-migration of undocumented immigrants not reflected in the Census Bureau estimates. Thus, the Census Bureau likely underestimated population growth in Arizona and its counties from 2000 through 2007 and overestimated the growth in subsequent years.
Note on missing data for all trended county data: La Paz County was created in 1982, as the then-existing Yuma County was split into La Paz County and a smaller Yuma County.