Weighted Density and No Zoning

If you don’t read Austin Contrarian there is a really good set of articles over there about weighted density. Basically, instead of just dividing the total number of people into the total area in which they live, you cut the area into slices, find the density of each slice, then average the slices based on how many people live in each.

To put it another way, suppose you select a person at random from a metropolitan area. How dense is their neighborhood? An average of these values would constitute weighted density, and would in turn provide an insight into how the average person lives.

If you followed the comments in my earlier post, I sort of guesstimated a population density of 6000 people per square mile inside Beltway 8, a commenter pointed out that it was more like 3900, and I realized that I was mentally excluding the large undeveloped areas as well as the substantial industrial development that exists along the Ship Channel.

Weighted Density provides a way to quantify that earlier guesstimate, by excluding those vast uninhabited areas. And whaddaya know. From a recent Contrarian post, here’s Houston and Austin:

Density hovers in the low 6000s as you travel outside Midtown and through the Montrose and the First through Fourth Wards. It drops to 5000 as you pick up the lower densities of large-lot neighborhoods like MacGregor, River Oaks, and the Heights. Then the density picks back up again as you get outside of the prewar gridded neighborhoods and into the land of large garden apartment complexes, which are some of the densest tracts in the city. Houston is level at about 6,000 people per square mile out to about 12 or 13 miles before steadily falling.

In other words, out to about Beltway 8.

Now rarely is the question asked, is our children learning why is Houston so much denser than Austin, given that Austin’s original housing stock was of the same basic type as Houston’s? The most simplistic answer is that Houston has just built a lot more multifamily housing, whether that’s greenfield garden apartments in Gulfton or Westchase or infill garden apartments in the Montrose or infill condos along Memorial and in Uptown and varying other places.

Austin, on the other hand, has tended to follow the more traditional American path of restricting everything to single-family at initial buildout, then later having awkward conversations and long and drawn-out meetings asking “where shall we increase density?” If you read the Austin Contrarian archives you’ll learn all about the VMU ordinance and exceptions to the VMU ordinance and neighborhood-by-neighborhood infighting over who’ll be “forced” to accept density. Against all this, one little fight over one Ashby high-rise seems like child’s play by comparison.

10 thoughts on “Weighted Density and No Zoning”

  1. What is that massive spike at ~45 miles outside of City Hall? The Woodlands? (it would make sense, wouldn’t it?)

  2. The Woodlands is the ~36 mile mark. That massive peak at ~47 is Galveston, which is a bit misleading since its so far away from the city limits. I guess that it was the cut-off mark. I imagine that in the 70s and 80s, more peaks would appear, like for Bryan-College Station and Beaumont.

  3. I would like to see graphs for other cities, like Phoenix or Atlanta or Miami, overlaid on Houston’s… Austin is a much smaller metropolitan area, not exactly comparable.

  4. I agree. The Austin metropolitan area (which is a relatively young metropolitan area as far as sprawl goes) isn’t a good comparison to Houston. To me, the argument of “look, Houston has no zoning, that’s why it has higher density” is bullshit. Not to say it isn’t true, but you can’t throw up a map comparing Houston to Austin as proof.

  5. Agreed. Do a comparison of Houston and Atlanta and I’ll buy it. That is Houston’s closest peer city – both are new, sprawling sunbelt cities and their metro areas are nearly the same size.

    Dallas or Phoenix might also be worthwhile comparisons, though they are smaller and the presence of Fort Worth complicates Dallas.

    Miami might also be comparable but the constraints of the Atlantic Ocean and the Everglades would manipulate the density.

    .Los Angeles might be meaningful too, but it’s much bigger.

    None of the other metros in the same population class are fair comparisons because they’re older cities.

  6. Do a comparison of Houston and Atlanta and I’ll buy it.

    But then I’d have to actually make my own graphs, instead of just ganking Austin Contrarian’s…

  7. You can go to the Census bureau spreadsheet and run your own city-by-city comparisons. Re: Houston vs. Atlanta: Houston is much denser than Atlanta. Atlanta is one of the least dense cities in the country. I calculated the weighted density of the 32 largest U.S. urbanized areas back in 2008, using 2000 Census data, and Atlanta was the least dense by a wide margin.

    I think it’s fair to compare Houston and Austin. Sure, past the 20-mile mark or whatever, the Austin graph is mostly picking up sparsely settled ranch land. But Houston is much denser between the 4-mile and 15-mile marks. Of course, a city should get denser as it grows. On the other hand, I’d also Houston’s sprawling highway network to push against high weighted density, while Austin’s limited highway network should push weighted density up. I think the difference in the density profiles is some evidence of zoning’s impact.

  8. Atlanta is strange, since the actual city limits has a population much lower than Austin’s. But we are covering the metropolitan area, not the city itself, so it would (probably) work.

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