Replacement was another idea we talked about in the population analysis class this week. Essentially it is an estimate of the deaths and migratory outflows from the area over a specified period of time and is called replacement because it is what you would need to replace in order for population to remain the same. Not really terribly complicated, but it is a nice complement to the idea of turnover and I generated both the level and the rate for counties in North Dakota.
So the level is not that interesting. Why? Well the major population centers end up being the counties that have significant need for replacement. In fact, they turn out to be the counties that can most easily make up this amount because, well, they are the major population centers. Those kind of go hand in hand as you would expect. Now the replacement rate takes this again into a replacement per 1,000 of population.
This is much more interesting. Notice that Cass County, the largest county in the state, is in one of the lowest replacement rate levels. That is because they are so large, so that even though they ended up needing a large absolute number of people it is not that large a portion of their population overall. The same holds true for Burleigh county, and to a lesser extent Grand Forks and Ward counties. It is interesting that the Southwest portion of the state, specifically Bowman, Hettinger, and Adams counties, are high on the replacement rate scale. Of more local interest may be the fact that Nelson county is also high on this scale as well.
There has long been a bit of a rural depopulation narrative for North Dakota. That combined with the population aging faster than the country as a whole led to treatment of North Dakota as a bit of a laboratory for economic impacts of aging stories for a variety of industries in the late 1990s and early 2000s. A decade of oil growth and development changed those narratives significantly, though maybe only as a temporary reprieve? The notion of oil wells as a fountain of youth has not seemed to catch on so I guess the hard work of sustainable growth and development, both in the economy and the population senses, must still be done.
One of the key things to consider here as well is an economic growth narrative as well. Like it or not, most of the higher growth counties over this time frame were also lower turnover rate counties. That is not a perfect correlation, but it surely passes the eye test and is even true in counties with universities which have a population more likely to migrate out in any given time frame.