Austin Contrarian

78704 and the 2010 Census

I wrote briefly a couple of days ago about the 2010 Census counts for a handful of central Austin census tracts.  I've now compiled the numbers for 78704.   (For those not from Austin, that's the zip code directly south of Downtown.  It is a large chunk of Austin's urban core.)

I'm mildly surprised.  78704 lost population.  I'm surprised because 78704 saw a significant amount of new construction over the decade.  But just mildly surprised, because the loss mainly reflects the loss of children in the area, something I expected.

Here are the raw population counts:

Thus, only three of 78704's Census tracts saw an increase in population.  Contrast 78704's 2.3% population loss with Austin's 20.3% gain over the same decade.

This hardly reflects a flight from the inner city, however.  78704 experienced steep increases in the price of housing between 2000 and the beginning of the recession, which shows there was healthy demand for housing in the neighborhood.  And developers did add a fair amount of new housing over the decade (click to enlarge):

The zip code grew its housing stock by 10%.  Every census tract but one added housing.  Some tracts added a significant amount of new housing:  tract 13.03 grew its housing stock by 20%; St. Edwards grew its housing stock by more than 33%.

The discrepancy between the growth of the housing stock and the loss of population is partly explained by vacant housing.  Only six of the eleven tracts saw an increase in occupied housing.  78704 on the whole had a higher vacancy rate in 2010 (9.6%) than 2000 (3.7%).  Austin was booming in 2000 and mired in a deep recession in 2010, so this should be expected.  But the vacancy rate is also partly due to the timing of new units entering the market.  262 of the vacancies in Zilker (tract 13.03) are in Barton Place Condominiums, which just entered the market in 2010.  The vacancy rate naturally will drop as the market absorbs this new construction.

2010's higher vacancy rate only partly explains the loss of population, however.  78704 did have 3.7% more occupied housing units in 2010, after all.  It just had fewer occupants per housing unit:

78704 dropped from an average of 2.1 persons per occupied unit in 2000 to an average of 1.97 persons per occupied unit in 2010, a 5.86% decrease.  By contrast, Austin saw a much smaller decrease (both in absolute value and as a percentage), from 2.47 to 2.43.

78704 saw this big drop in persons per occupied housing unit because it lost a lot of children between 2000 and 2010.  In fact, all of the population loss can be traced to the loss of children.

If we disaggregate the population into children and adults, we see that 78704 lost 1,387 children and added 385 adults.  Put differently, 78704 shed 17.9% of its population of children even as it saw a slight increase in its adult population.   That's a huge decline, percentage-wise, for just one decade.  That decline is also reflected in the change in the number of children per occupied housing unit.  The average number of children per occupied housing unit shrank by 20.9% between 2000 and 2010.  By contrast, the number of children per occupied housing unit in Austin as a whole actually increased slightly (from 0.56 to 0.58) between 2000 and 2010.

Austin continues to sort itself by household type:  families with children to the 'burbs; singles and couples to the central neighborhoods. 

Some population numbers

I've been itching to calculate weighted densities using the 2010 Census data but, alas, I cannot yet.  The Census Bureau has released the 2010 Census redistricting data, which includes census-tract data.  But calculating a city's weighted density requires a list of all of the census tracts within the city's urbanized area.  The Bureau has not yet released the data for urbanized areas (or, if it has, I cannot find it).  

I'm left to speculate until the Bureau releases the full data files.  My bet is that Austin's standard density (the population of the urbanized area divided by the land area) has increased but its weighted density has decreased.   Just a guess.

We do have statistics for individual census tracts so there is no need to guess there.  I'm struck by how uneven growth has been in the central core.

Take census tracts 6.03 and 6.04, which comprise West Campus.  In 2000, tracts 6.03 and 6.04 had 5,273 and 5,199 inhabitants, respectively.  In 2010, they had 7,793 and 6,496, respectively.   This was a 36% increase in population.  This really is remarkable growth.  Austin's population grew by only 20.4% (656,562 to 790,390).  Tracts 6.03 and 6.04 were already two of the city's densest in 2000 while I'll wager most of Austin's growth occurred in greenfields.  It is harder to grow a built-out area's  housing stock by 5% than it is to grow a cow pasture's housing stock by 5%.  This shows that it is possible to accommodate population growth with infill development.

Downtown's population also boomed.  Census tract 11 (which includes downtown and Rainey Street) more than doubled in population, from 2,386 to 5,512.  This growth is less impressive to me than the West Campus growth, though.  Downtown has (or had) lots of undeveloped land that easily could be developed as residential.  West Campus did not.  

The central core's growth was uneven, though.  Take the Zilker (tract 13.03) and Bouldin Creek (tract 13.05) neighborhoods directly south of Downtown.  The population of both neighborhoods actually declined.  Zilker dropped from 3,022 to 2,871 and Bouldin Creek dropped from 5,659 to 5,488.

Part of the decline is surely due to the recession.  Bouldin Creek added 232 housing units between 2000 and 2010 but it had only 88 more occupied units in 2010.  The Zilker neighborhood added 334 housing units between 2000 and 2010, but it had only 56 more occupied units in 2010.  There were a lot more vacancies in both neighborhoods in 2010.

But each still had more occupied units in 2010.  The declining populations are due to declining household sizes.  In 2000, the average Bouldin Creek household had 2.18 members; in 2010, 2.04.  The average Zilker household shrank from 1.94 members to 1.78 members.  

Zilker and Bouldin Creek illustrate that it takes a pretty signficant amount of new construction just to maintain the status quo in these central neighborhoods.  It should be no surprise to anyone that singles and couples continue to displace households with children in these central neighborhoods.  Given that trend, these neighborhoods must add a lot of new units just to maintain the same population.   If Bouldin Creek had the same occupancy rate it had in booming 2000 but with 2010's average household size, it's 2010 population would have been 5,751, just 1.6% greater than 2000's total of 5,659.   Those 232 new housing units were barely enough, in other words, to maintain its population.  (Zilker would have seen a 10% population growth using 2000 occupancy rates and 2010 household sizes.  Better, but not great.)

The numbers for Zilker and Bouldin Creek explain my prediction that Austin's weighted density declined between 2000 and 2010.  I'm betting that most of the core neighborhoods -- the densest neighborhoods -- are like Zilker and Bouldin Creek rather than West Campus or Downtown

 

Links

Two to pass along:

NeoHouston has a great piece comparing the street interfaces of good urbanism and bad urbanism, with a nice use of Houston projects to illustrate his point.

Julio Gonzalez at Keep Austin Wonky argues against Austin "exceptionalism"; i.e., perhaps we're not as great as we thing.  A nicely contrarian piece.

I like his conclusion but am less confident about his analysis.  He runs a regression purporting to show that, among Texas cities, Austin's median household income is low given its high share of residents with masters, professional  and doctoral degrees.    My criticisms:  (1) he  should run his regression on metropolitan areas rather than municipalities because high-wage earners tend to cluster together in exclusive suburbs (this would require using a national panel since there aren't enough Texas metropolitan areas); (2) he should use gross metropolitan product rather than household income; and (3) we should keep in mind that Austin has an unusually high proportion of masters and Ph.D. because of UT; it is an outlier. 

1990 versus 2000

Following up on my entry on neighborhood "tipping points":

Commenter Nick pointed out that the maps of Austin I posted there use 20% class breaks, which perhaps causes them to exaggerate the degree of segregation.  For example, two census tract will have the same shading even if one is 19% African-American and the other 1% African-American.  That's a fair point (although the class breaks do a good job of showing census tracts in which  African Americans and Hispanics predominate.)

So I generated a couple of new maps from the Census website.  They show, for 1990 and 2000, the percentage of African-Americans residing in each block group in central, south and east Austin.  (Click the maps to enlarge.)

I generated the 2000 (second)  map first and let the Census mapping tool generate natural class breaks, which explains the weird ranges.  I then used the same class breaks for the 1990 map.  

 

The maps speak for themselves, but three fairly obvious observations:

1. Things didn't change much west of I-35 between 1990 and 2000.  A handful of block groups saw a rise in percentage of African Americans, more saw a decline, and most saw no change.

2.  In 2000, African-Americans made up a low (<7.4%) or very low (<3.4%) percentage of most central and south Austin block groups.  Central Austin north of Lady Bird Lake had the largest concentration of block groups with a very low percentage of African-Americans.

3.  Things changed more dramatically east of I-35.  The heavily African-American block groups tended to shift east, away from I-35.

N.B.  These maps do not necessarily imply that the absolute population of African-Americans dropped in a particular block group -- the block group simply may have added a lot of residents of other races.  

Tipping points

Here are a couple of interesting pieces on  the "tipping point" theory of racial segregation.

Why do racially-segregated neighborhoods exist and persist?  The standard explanation  is that whites don't like to live near, say, African-Americans; when African-Americans start moving in, whites start moving out.  Real estate agents steer whites away from African-American neighborhoods and vice versa.  And let's not forget the legacy of de jure segregation, which herded African Americans into a few neighborhoods; residential patterns typically change slowly.  The standard explanation relies on more or less overt, conscious racism.

There's clearly some of that going on.  Most cities -- Austin included -- had either de facto or de jure rules that relegated African Americans to just a few, exclusively African-American neighborhoods.  Although I consider Austin a fairly racially tolerant place today, it is still  strikingly segregated:

Density and congestion, etc.

Whenever I see new data on cities, I'm always tempted to match them to the cities' weighted densities, if for no other reason than no one else does it.  And so with the Texas Transportation Institute's latest report on city congestion.  TTI found a wide range in hours lost due to congestion per year -- e.g., in 2007, Lost Angeles drivers lost an average of 70 hours per year to congestion;  Cleveland drivers, just 12.  (The relevant TTI table is here  (pdf).)  Does weighted density partly explain this variation?

The answer is "No," based on my admittedly simplistic analysis.  

Below the jump I have three charts plotting, for 33 cities, weighted density, standard density and total population against hours lost per traveler to congestion.   (The 33 cities include the 31 largest urbanized areas -- excluding New York City, which is always an outlier -- and Austin and Honolulu.) 

As the scatter plot shows, weighted density explains virtually none of the variation in congestion (adjusted R² = .06).   Standard density explains a bit more  (adjusted R² = .19).  And total population, a bit more than standard density  (adjusted R² = .28). 

Punching above its class

The Texas Transportation Institute has issued its annual report on congestion in American cities.  As usual, Austin doesn't do well, punching well above its class.  Tthe average Austin traveler experienced an annual delay of 39 hours in 2007.    That's up from 32 hours in 1997, although no worse than 2006.   

Ryan Avent puts the Austin figures in perspective:

The average traveler in the New York metro area faces 44 hours wasted per year, for instance, while the average traveler in Los Angeles loses 70 hours per year to congestion, even though New York’s metropolitan population is much, much larger than LA’s.  More interesting still, Austin and Raleigh aren’t that far behind New York with 39 and 34 hours wasted annually, despite the fact that both metro areas have less than two million people while greater New York is home to 20 million people.

TTI also calculates the percent of peak period travel that is congested.   Austin again fares poorly -- its roads are congested for 70% of the peak travel period: 

By comparison, Dallas's roads are congested for only 66% of the peak travel period.  Houston is marginally worse at 73%.   Austin's peers include New York (69%), Detroit (71%) and Baltimore (69%).  

One has to wonder what damage Austin's congestion has wrought to downtown.   Businesses want to locate where their employees can get to them, and high peak-period congestion means that commuters must fight traffic to get to work most of the time.   I suspect Austin's downtown suffers more heavily from peak-period congestion than any other employment center in the area since MoPac and I-35 -- downtown's principal commuter routes  -- are the two most congested roads in the area.     Eventually we must recognize that our congestion will stunt downtown's growth, if it hasn't already.   We wil lose the economies of scale and agglomeration benefits that a vibrant downtown would  yield.

You know, of course, that there is only one solution.

Skilled cities II

While I'm in this nerdy mood, let me point to this paper by Jaison Abel, Ishita Dey and Todd Gabe:

We estimate a model of urban productivity in which the agglomeration effect of density is enhanced by a metropolitan area’s stock of human capital. Using new measures of output per worker for U.S. metropolitan areas along with two measures of density that account for different aspects of the spatial distribution of population, we find that a doubling of density increases productivity by 10 to 20 percent. Consistent with theories of learning and knowledge spillovers in cities, we demonstrate that the elasticity of average labor productivity with respect to density increases with human capital. Metropolitan areas with a human capital stock that is one standard deviation below the mean level realize around half of the average productivity gain, while doubling density in metropolitan areas with a human capital stock that is one standard deviation above the mean level yields productivity benefits that are about 1.5 times larger than average.

This is a little technical, so let me translate:   Cities tend to become more productive as they grow denser.   On average, a city's workforce becomes 10% more productive when the city doubles in density.   But that average obscures the importance of skills.   Less skilled cities benefit a lot less than skilled cities from densification.   In fact, skilled cities, on average, enjoy three times the productivity gain from denser growth than less skilled cities.   This is yet more evidence of the increasing returns and agglomeration benefits from density.

This is a nice complement to the Glaeser and Resseger paper.  Glaeser and Resseger found that workers in skilled cities become more productive as the city grows, while workers in unskilled cities do not.   Abel et al find that workers in skilled cities become more productive as the city grows denser; workers in unskilled cities, less so.

The authors also test their conclusions using a variant of weighted density. They find even greater productivity gains (20% on average) when a city doubles its weighted density.

The authors use a coarse form of weighted density.  They weight urbanized area density by county subdivisions.  But how you chop up a city matters when calculating weighted density.  In order to calculate weighted density, you first divide the city into a bunch of smaller regions.  You then assign each region's density a weight equal to its share of the populations.  In general, weighted density increases as you chop up the city into smaller regions.

I used census tracts for my weighted densities.  There are many more census tracts than county subdivisions.  I thus got a lot more stratification than they did -- e.g., their top weighted density was 19,000 ppsm, while mine was 33,000.  How you divide a city for calculating weighted density is somewhat arbitrary, but I think using census tracts makes more sense than county subdivisions, which are more or less arbitrary.  I suspect the authors would have found even greater returns to density had they weighted density by census tracts rather than by county subdivisions.  

H/t Richard Florida.

City growth

The Census Bureau has released its July 1, 2008 city population estimates.  Note that Texas has three of the largest eight (Houston, San Antonio and Dallas) and six of the largest 21 (add Austin, Fort Worth and El Paso).  Houston now trails Chicago by just 600,000, a gap that Houston could close within 20 years if the last decade's growth rates hold.  This is a surprising statistic as long as one ignores metropolitan populations, which are what really count when calculating a city's heft.  Chicago's metro population is still much larger than Dallas and Houston's, which are probably now the fourth and fifith largest metro areas.  And, in general, Texas cities have large boundaries and aggressively annex surrounding areas, which partly accounts for their rapid growth.

What's going on with Fort Worth? It had the fastest growth of the top 25, both between 2007 and 2008 (3.6%) and between 2000 and 2008 (29%).  No other city in the top 25 was close; Charlotte and Phoenix were the closest at 21% and 18%, respectively.  Fort Worth has grown twice as fast as Austin since 2000.  I haven't heard much about Fort Worth's explosive growth.  Strange.

One surprise on the other end:  Philadelphia contracted at a faster rate than Detroit between 2000 and 2008.

The most noteworthy fact here may be that, as the WSJ points out, central cities did very well between July 1, 2007 and July 1, 2008.  

The central-city population in U.S. metropolitan areas with more than one million people (excluding New Orleans) grew at an annual rate of 0.97% between July 2007 and July 2008, compared with a growth rate of 0.90% in 2006-2007, and growth rates around 0.5% in the years between 2002 and 2005.  By contrast, U.S. suburbs in metro areas greater than 1 million people grew at a 1.11% annual rate in 2007-2008, down from growth rates between 1.29% and 1.48% between 2002 and 2005.  Central cities are closing the gap.

The WSJ attributes the shift in growth rates to the recession.  We have a short memory.  2007 was the year of the historic spike in gas prices.  Central cities -- especially older, monocentric cities like Chicago -- began to look a lot more attractive to commuters.  I imagine this played a much bigger role than the nascent recession.   

Nothing to see here

The Census Bureau has released a new report (pdf) comparing the growth of Metropolitan Statistical Area central and outlying counties between 2000 and 2007.

Wendell Cox says the report shows "that the nation continues to suburbanize, despite the consistent media 'spin' that people are leaving the suburbs to move to core cities."

[T]he conclusion of the new report is clear. The nation’s most remote suburbs – its exurbs – are growing much faster than the central counties. Whether this trend will now reverse, of course, is up to debate. Perhaps demographic changes and higher energy costs will slow expansion on the outer fringes. More likely, the current recession may well lead to less exurban growth, but history suggests this may prove only a short-lived trend.

My own take is that this report offers little meaningful information other than growth and migration rates for the MSAs as a whole.  Breaking out the numbers for central counties and outlying counties tells us little because the Bureau defines "central counties" expansively as those containing all or a substantial portion of the MSA's urbanized area.   Since a city's urbanized area can and often does stretch across several counties, the Bureau's definition sweeps up counties that we typically consider suburban.  For example, Travis and Williamson are "central counties" in the Austin-Round Rock MSA, even though Williamson is the quintessential suburban county.   (Hays is considered an outlying county, but will almost certainly be a central county in the next census due to the rapid spread of Austin's urbanized area.)

Because of the broad definition of "central" counties, almost all MSA population is "concentrated" in these counties.  In MSAs with more than 5 million, for example, 97.4% of the population lived in central counties (2007 estimates).  For all MSAs, the number is 91.8%.

Naturally, because central counties began with a large baseline population, even large absolute increases in population yielded smaller percentage increases than small absolute increases in the less populous exurbs.   For example, in the Midwestern MSAs, the outlying counties grew at nearly twice the rate of the central counties.  But the central counties added 5 times as many people.   The New York-Northern New Jersey-Long Island MSA is an even more extreme example.  Its central counties grew by 2.6% between 2000 and 2007 while its outlying counties grew at an explosive 26.6% rate.   But the central counties added 480,000 people to just 12,000 for the outlying counties, 40 times as many.

For the United States as a whole, MSA central counties added nearly 17 million people compared to 2.4 million for outlying counites.  Central counties in the northeastern region (which includes New York) added nearly 1 million while the outlying counties added fewer than 24,000.  The South Region's outyling regions added the most by far -- nearly 1.8 million -- but even here the outlying growth was dwarfed by the 7.7 million added by the central counties.   

If the Bureau's goal was to tell us something important about the relative growth of exurbs and central cities, it failed.   There's just not much to the data because of the overly-expansive definition of central counties.   As Wendell points out, this report might very well understate suburban growth (in fact, this is almost certainly true), but this report doesn't shed much light on the question.  Wendell himself recognized this limitation on the data, but unreasonably, I think, attempted to draw an unwarranted conclusions from the report anyway.