A couple months ago, Sarah Goodyear showed us a sprawl ranking of U.S. metros (and explained why we should care). Those rankings, based on a four-factor "Sprawl Index," do a good job capturing a snapshot of sprawl in time. What they can't do is speak more directly to the recent policies a city has taken to change its growth pattern. They can see if the metro has sprawled, in other words, but not if it's sprawling.
A new report from Reid Ewing and Shima Hamidi of the University of Utah, lead researchers on the aforementioned rankings, gets at that question. Ewing and Hamidi scored the largest 162 U.S. urbanized areas on the Sprawl Index — or, if you're feeling optimistic, the Compactness Index — for 2010. (Urbanized areas reflect development better than fixed metro area boundaries do.) Then they applied the index to the same cities in 2000 to show the change over time.
Here's the scene in 2000 (the darker the splotch, the more compact the area):
And here it is in 2010:
Unfortunately the individual city shifts are a bit hard to discern on the maps created by Ewing and Hamidi. So I took the report's supplemental data and calculated the change in the Sprawl-Compactness Index from 2000 to 2010 for all 162 urbanized areas. The results cast the earlier metro area rankings in a slightly different light.
Here are the 10 most compact urban areas in 2010, according to the new report:
And here's how those same 10 cities changed on the index since 2000. Positive figures reflect an increased compactness index (i.e. smart growth); negative ones reflect a decrease (i.e. sprawl):
So now what do we see? San Francisco-Oakland still tops the charts, but it appears to have sprawled a bit over the past decade. New York has moved the needle in the right direction, but not much. Laredo remains a top city despite a pretty dramatic slip in compactness. Ewing praised Los Angeles as the "biggest success story" when chatting with Goodyear, and for sure its change is impressive, but Reading nearly doubled L.A.'s score increase and Oxnard beat it, too.
Now let's take a look at the other end of the list. Here are the 10 most sprawling urbanized areas in 2010:
And here's how much these areas changed on the index since 2000:
Here we see that even toward the bottom of the Sprawl Index, several cities have been heading in the compact direction — most notably, Chattanooga. Charlotte and Greenville, meanwhile, continue to fade. Sprawl in Atlanta was somehow worse in 2010 than it was a decade ago; interestingly, though, Atlanta seems to have sprawled less than the San Francisco-Oakland area since 2000.
Now let's take a look at the most dramatic changes during the period in question. Here are the urban areas with the biggest index increases from 2000 to 2010 — meaning the cities that gained the most compactness:
When it comes to promoting compact growth between 2000 to 2010, Tallahassee laps the field, at least as far as the Sprawl Index is concerned. Washington's place on the list isn't a surprise, especially considering its place in Maryland's smart growth plan. (To that end, Baltimore's index increase of nearly 9 points is also notable.) Some areas are less intuitive — looking at you, Mobile. Other cities making significant jumps include Minneapolis (8.3), Seattle (8.1), Madison (5.7), and Houston (5.3).
Finally, here's a look at the urban areas that sprawled the most between 2000 to 2010, according to the index (ignore the 0 at the bottom):
Stockton (aka "Foreclosureville") certainly makes sense on this list, considering the hit it took after the housing bubble burst. Austin is a bit of a strange sight, however; Texas in general leaps off the chart. Other notable declines include Phoenix (-12.6), Indianapolis (-12.4), Cleveland (-11.4), and Denver (-9) — the latter a big surprise, considering its recent efforts to reduce sprawl and promote density.
Which brings us to the caveats. It's possible that cities showing the greatest gains in compactness over this time period deserve to have their policies studied and emulated. It's also possible this particular time window isn't the best one for certain areas. And it's yet also possible the outlier cases are a sign that the index itself needs further adjustment.
It's also worth keeping in mind that these figures aren't percentage increases or decreases; they're a rise or fall in index scores. A full understanding of that change requires a closer look at the four metrics that inform the index — density, land use mix, activity centering, and street accessibility.
Still, as another way to evaluate city growth policies, changes in the Sprawl Index deserve our attention. Ewing and Hamidi report that, as a general rule, the urban areas that were compact in 2000 remained compact in 2010, and vice versa for those that were sprawled. Overall, sprawl increased during the decade — "but only slightly," they conclude. It may take another 10 years to know which way the momentum is heading.