Monday, May 18, 2015

Is the city of Pittsburgh growing?

While the civically obsessed await the results from the off-year election going on, here is a question for later in the week. Is the city of Pittsburgh growing?

Scheduled to be released this week is the latest annual data point for population in the city of Pittsburgh as of July 2014.  Last December 2014 population estimates for the nation and individual states were released. In March the comparable 2014 data for individual counties and metropolitan areas came out. What will come out this week completes the data trifecata for the year with population estimates for individual municipalities to include the city of Pittsburgh.

Whether the city of Pittsburgh is growing is a matter of moderate public debate and I assure you everyone has some very strong ideas on whether the population trends in the city are positive or negative, and as often as not debate with references to regional, county and city population trends conflated to the point of confusion. But looking to the future this is an important thing with a mayoral goal I hear about of growing the city by 20,000 over a coming decade, though the starting point for that calculation seems to keep slipping. Population growth has also been at least implicitly part of the debate over what impact things like the Pittsburgh Promise can have on the city of Pittsburgh.

What do we think we know?  For sure the city of Pittsburgh has been declining in population since the 1930s.  Some say since the 40s or 50s, but population growth recorded between 1930 and 1940 is really the result of some annexations that expanded the geography of the city of Pittsburgh. Account for that and the actual population in the city of Pittsburgh proper was already pushing downward back then.  Yet a few years ago the buzz was about the first recorded population increase for the city of Pittsburgh in many many decades when estimates for 2011 showed population increase between 2010 and 2011.

To oversimplify a complicated subject, these annual population estimates become ever more problematic the smaller the scale of geography. So municipal level population estimates have issues that are not so bad at county, MSA or state levels. A case in point is the population increase first observed for the city of Pittsburgh between 2010 and 2011 per the news in the previous link.  You may read my contemporaneous moderation in talking about the growth estimated at +1,780 that year. It just did not seem right and I knew the numbers would not hold up.

Indeed in revisions the very next year, the population growth over that same period was re-estimated to be only +392, or 77% smaller than originally reported.  A much smaller, but still positive, change, and for the city of Pittsburgh even population stabilization is a pretty big story.  The revision I can explain in multiple ways having to do with data revisions to some college dormitories numbers in the city and also due to some temporary methodology changes the Census folks used that year, but soon abandoned.

For the city of Pittsburgh the data picture gets more conflicted actually.  The primary data input for population estimates for individual municipalities is the population change for the counties where they rest. The previous year's data on population change (between 2012 an 2013), Allegheny County was estimated to have increased by +2,579 , but the city of Pittsburgh was estimated to have returned to decline of 348  This year, we already know the estimated population change between 2013-2014 for Allegheny county is actually a decline of 1,698, so the estimated change for the city of Pittsburgh is going to be negative, the question is really just by how much. We can debate ad nauseam how close the estimated get to ground truth.

 There is a side story to all of this of note. As mentioned here in the past, the main input to the municipal level breakdown of population change within a county is the pattern of building permits issued by municipality. One odd thing discussed here in the past is that the data the city of Pittsburgh itself reports on the number of building permits has zero in any multiple unit structures between 2005 and 2013. Since it seems pretty obvious there were building permits issued for new multiple unit structures, you have to wonder if the population estimates that resulted were biased downward in some way. The census methodology is only as good as the data it uses, and the building permits data is self reported by municipalities so if true the city only has itself to blame in some way. It looks like that might have just changed with the latest building permits data for the city reporting a new 215-unit building permit issued in December 2014.  Then there is an even more complicated subject over whether housing unit conversions are property recorded in the data for the city.

I won't even begin to go into natural population trends impacting the city of Pittsburgh.

Yes, I could go on.. but enough yes?


Anonymous BrianTH said...

It is never enough! (for those of us who actually care about this stuff.) And that building permit story specifically is a mystery I would still love to solve.

Anyway, I'll just toss in my favorite point these days, which is that headline population numbers aside, the REAL story is the massive amount of underlying change in composition.

The more or less flat population total conceals a lot of exits and entrances (which are currently more or less in balance, hence the overall flat total). And the composition of the exiting population is very different from the entering population. Of course this is true for births and deaths ("natural" change) as a matter of course. But with offsetting in-migration and out-migration playing such a large role as well these days, it is driving compositional change much faster than such natural change.

Hence the big differences in things like educational attainment by age (something Chris has well-documented). And all that also help explain why some parts of the City seem to be changing so dramatically (including with respect to things like rent and housing prices), whereas others seem to be continuing the same slow decline. It even feeds into the current political dynamics in the City (a relevant topic as I write this). All that is really a function of where compositional change has been concentrating.

Tuesday, May 19, 2015 12:23:00 PM  
Anonymous Michael Lamb said...

The composition change creates some interesting dynamics, statistics and questions. As more young people(students and employees) and empty-nesters move in, young families with school age children continue to move out. It creates positives like higher median incomes and negatives like declining school district enrollment.

Can a city thrive when children are so scarce? Can a city like that is becoming so much more expensive be a welcoming place for international immigrants? How do "affordable housing" initiatives fit in?

Interesting stuff.

Wednesday, May 20, 2015 1:12:00 PM  
Anonymous Anonymous said...

I do wonder what impact the documented issues in the City's building inspection department might play in the statistical confusion. Until the current regime, the process of getting permits was byzantine, at best. Plus, if all the census folks are looking at are permits for new buildings, then that would ignore all the repurposing going on downtown and other areas (add to that the permits for that work would not necessarily indicate "multi-family" depending upon the type of work being done). Doubt this explains everything but something to keep in mind.

Thursday, May 21, 2015 11:31:00 AM  
Anonymous BrianTH said...

So all large cities tend to pump in single young adults and then pump many of them back out when they start forming families. This is going to be all the more true of cities with strong universities, and also cities which are relatively small in land area such that many of the closest-in, semi-urban communities are in first ring suburbs. But there is still a certain percentage of those young adults that will actually stay in the city even as they form families (although that is an oversimplification as there will be some young families migrating into the city as well--but for the purposes of this discussion it simplifies things to think of this as just the same population moving through time).

Obviously, one thing you can do to get more young families is to increase that percentage. But at least potentially, you can also just increase the inflow of single young adults, and if the percentage sticking around remains the same, you will then get a higher number of young families down the road.

But that notion in turn is complicated by the fact that the percentage sticking around might vary in response to the initial inflow of single young adults. One plausible hypothesis is that more single young adults will lead to more amenities, lower crime, more investment, more jobs, better infrastructure, and so on that will make cities even more attractive to young families. Another hypothesis is that single young adults will drive up housing prices and lead to changes in neighborhood character that further discourage young families.

Exactly how that works may ultimately depend on things like housing policy. Note by far the most effective affordable housing policy is just to have a lot of housing supply, which means making it easy to build a lot of new units--constrained housing supply will artificially drive up prices, and even if you set aside a small percentage of subsidized units, that can necessarily only help a small percentage of households.

Generally speaking, though, the evidence seems overwhelmingly in favor of more single young adults actually making city neighborhoods more attractive for young families. So, for example, in Manhattan as various neighborhoods have become newly-popular residential locations for young professionals, a "baby boom" has usually followed. That doesn't solve all the demographic problems for cities, but it is usually the neighborhoods where new people and new investments are located that birth rates will be increasing, whereas it is in other stagnant or declining neighborhoods that birth rates will continue to fall. In that sense, the sort of young families who actually might consider living in the city at all seem to overlap more than diverge with single young adults when it comes to desirable neighborhood characteristics.

Exactly how this plays out for something like the Pittsburgh School District is even more complicated, because even more young singles eventually leads to more young families, they may be the type of families more likely to look at charter schools, private schools, and so on. But I do think it is more likely than not that even as the City continues to lose newly-formed young families to the suburbs every year, it will also be accumulating more young families as a result of capturing some small but steady, and perhaps even rising, percentage of its increased inflow of young singles.

Thursday, May 21, 2015 1:20:00 PM  
Blogger C. Briem said...

the building permit data the census uses for this is self-reported data from individual municipalities. So if there are building permits not going into the estimates calculation, it is because the city didn't include them in the data submitted.

Thursday, May 21, 2015 9:14:00 PM  
Anonymous Anonymous said...

Alls I knows is, I'm still here.

Friday, May 22, 2015 9:22:00 AM  
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Sunday, September 18, 2016 9:16:00 PM  

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