The nation's most urban counties grew by a substantial 5.3 percent between 2010 and 2015, faster than any other type, according to a Demo Memo analysis of the Census Bureau's 2015 county population estimates by Rural-Urban Continuum. Counties in smaller metros grew at a slower rate, and those in rural areas lost population. Every component of population change is driving the growth of the most urban counties...
Natural increase is greater in big-city counties. Between 2010 and 2015, the rate of natural increase (defined as births minus deaths) was 2.8 percent in counties ranking 1 on the Rural-Urban Continuum (in metro areas with populations of 1 million or more). This was a higher rate of natural increase than any other type of county on the continuum. Counties ranking an 8 or 9 (the most rural) had a negative rate of natural increase, with deaths outnumbering births.
International migration is greater in big-city counties. Between 2010 and 2015, the rate of net international migration was 2.3 percent in counties ranking 1 on the Rural-Urban Continuum. International migration was positive in every type of county, but the rate was lower in less urban counties and was lowest (0.2 percent) in counties ranking 8 or 9.
Domestic migration is greater in big-city counties. Between 2010 and 2015, the rate of net domestic migration was positive only for the most urban counties, ranking 1 or 2 on the Rural-Urban Continuum. Less urban and rural counties lost more domestic migrants than they gained.