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:
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.