Population estimates are now trickling out and will continue to be released by the U.S. Census through next summer. Population estimates take into account births, deaths, and migration. As migration has slowed, demographers have focused more on what is called naturalized increases, which is the excess of births over deaths. However many counties are now experiencing naturalized decreases where deaths have exceeded births. This N.Y. Times article suggests more than 1,200 counties experienced naturalized decreases in 2016 and 1,700 have experienced at least one year of naturalized decreases in the past decade.
Further, this phenomena has taken on a very regional tone. We calculated naturalized decreases for counties where birth data is available (excludes small rural counties) and plotted it. As indicated in the map below based on larger counties, the naturalized decreases have been concentrated in the northeast and mideast regions. As you look more closely at the map, cities like New York and Boston appear largely unaffected, but the impact is in what the article calls outer suburbs. For example, Allegheny County, the county surrounding Pittsburgh has had naturalized decreases for ten straight years.