I grew up in Raleigh, North Carolina, the state capital and seat of Wake County, which contains several other municipalities.
When I was in middle school in the year 2000, I would have laughed if you had told me any of the following:
- The county’s population would grow by 43.5%, from 627k to 900k, in the next ten years.
- The county’s population would actually reach 1 million in the next fifteen years.
- Cary would become the seventh-most-populous municipality in North Carolina.
- Holly Springs and Fuquay-Varina would be considered reasonable suburbs to Raleigh.
- By 2017 Wake County would have 172 public schools (27 high schools) for 155,000 students.
Well, here we are. Wake County and Raleigh have made a million of those “best places to live/work/retire” lists since the year 2000, and the county has seen growth that puts it in the top ten or fifteen fastest-growing counties in the country, depending on how you measure.
So what does that rate of development look like on a map of land parcels? Good question, keeping reading for more…
The state maintains a shapefile download page for property parcels for every county (actually it looks like Lee, Richmond, Tyrrell, and Wayne counties are missing, based on the listed file size).
The shapefile has a field called STRUCTYEAR that represents the year that structures were built, so with that we can construct a timelapse of development in the county.
The GIF that follows highlights how construction has proceeded by decade since just before the civil war.
For each ten-year period, new construction is highlighted in red, while previously existing construction is shown in dark gray.
The cumulative area of parcels featuring some form of construction starts off growing rather slowly, below 1% until the 1900s, and then hits several boom periods, eventually reaching 50% by 2009.
It’s fascinating to me that in the county of the state capital was so sparsely developed even well into the 1900s. You can also clearly see several different booms: downtown Raleigh expands in a burst in the 1950s and 1960s, then north Raleigh and Cary in the 1980s and 1990s, followed by the outer suburbs in the 2000s and 2010s.
It almost looks like there’s no space left when you glance at the 2017 image, but still almost 50% of county lots by area don’t have a structure according to the shapefile.
I think it might be interesting to do another animation for individual years from 1990-2017, since so much changes over ten-year intervals. With yearly transitions we might be able to see neighborhood-scale growth.
It was really easy to create all of these decade-specific images in QGIS by using layer variables – change the
@cutoff_year variable, let the map render, then save an image. The last step is tying them all together into a single GIF using GIMP.
Now, there are plenty of caveats to this:
- The shapefile documentation does say that the STRUCTYEAR field represents “the year of construction for the primary building on the parcel.” Since many very old buildings may have been replaced or now have newer buildings on the property, the early decades are probably underrepresented.
- Lot size has a disproportionate visual impact. Obviously RDU airport is a big deal in terms of land area, and its construction visually outweighs hundreds of tiny lots being built up near downtown.
- The map doesn’t differentiate between residential, commercial, and governmental construction. That’s a point of analysis worth exploring in another post – is residential or commercial building the real pioneer? Which one follows the other?
But what does this look like at the level of individual cities and towns?
For context, Wake County has 350,790 land parcels, according to this shapefile, of which 265,157 (75.6%) are within the boundaries of a municipality (that does not mean 75.6% of the land area is within a municipality!).
Raleigh is obviously the largest, but you can see the others distinguished by color in the following map:
So what if we look at growth over time by municipality – let’s start by hollowing out the 2017 municipality borders, and filling in lots over time using the same STRUCTYEAR field (note that means that not all of the white area will be filled in by 2017, as some lots have not yet been constructed on).
This is a pretty simple exercise with an attribute filter:
What’s It All Worth?
We’ve looked a lot at land by area and the binary status of whether or not it has a structure, but most people care more about land value than area. We still need to account for area though, since it’s a critical driver of value – so I created a new field containing the parcel value (PARVAL) divided by area (GISACRES) to yield value per acre.
Unfortunately we can’t look at value over time, since we only have value at the most recent appraisal. Let’s start with the whole county, and in this map, higher values are hotter colors. So dark blue is the lowest value, and the bright yellow downtown is the highest.
Look at the massive swaths of eastern Wake County that are dark blue. It’s not surprising that more rural areas have lower value per acre, but it’ll be interesting to see if development picks up along the relatively new US-264 bypass (in the red box) the way it has along other major highways that have been around longer (I-540, US 1 and 401).
What if we zoom to Raleigh (roughly):
I didn’t account for very small lots driving a high value-per-acre. I think we have to assume a floor on the value of a decent and inhabitable house, so if you can build a basic house on a tenth of an acre, you can get a higher value-per-acre than a modestly more expensive house on a lot more land. See clusters like Hedingham highlighted by the red box.
And now zooming to just the I-440 Beltline (ITB, if you know what I mean?):
Look at the Five Points and Glenwood Avenue areas (old money, for those not from the area) as they merge into very-high-value downtown, and then into Southeast Raleigh (less money, for those not from the area).
It’s a fascinating gradient – Raleigh had old, inexpensive neighborhoods ready for gentrification, but my off-the-cuff intuition says that there was so much other land available that people didn’t bother. Developers built new neighborhoods, people moved in, and the poorer neighborhoods stayed poor. Will gentrification come now that open land is running out in the rest of the county?
Just for fun, one more, focused on Five Points and downtown:
Fun fact: the highest number of structures on one parcel is 96! But only 412 parcels have 10 or more structures.
That’s all for now, but I’m hoping to work on several follow-up posts in the near future:
- Year-by-year animations of development focused on the interval 1990-2017.
- Does commercial development follow residential, or vice versa?
- More detailed analysis of the land value gradients and their relationships to major highways.
There has to be a consultant angle, right?
Sometimes maps and the right data can answer your business questions better than a spreadsheet – if you’re interested in a more in-depth analysis of how geography impacts your business, contact me and let’s talk.