Sunday, May 14, 2017

Is the City of Pittsburgh growing? Or not?

So in a week and a half we will get the latest dump of municipal level population estimates for the nation. The primary interest here is likely to be the latest datapoint on population trends for the City of Pittsburgh. Why? There is an ongoing meme that the City of Pittsburgh is growing. But is it?

Undisputed is that the City of Pittsburgh has pretty much been shrinking unabated for over seven decades. Some say the City stopped growing in 1950, but parsers before me figured out that actually the most of the growth the city of Pittsburgh experienced in the 1930s and 1940s was due to municipal annexations. Net that out and decline may go back at least to 1930. Nonetheless, a long time.,

So you can see why some might make a big deal of the first big sign that the City of Pittsburgh might be growing came with the release of population estimates for 2011. You can see the story from that time that pretty much has generated the persistent idea that the City of Pittsburgh is growing. PG: (July 2, 2012) Census data shows unusual rise in (City of) Pittsburgh population.

Basically there was at the time a pretty noticeable net gain of 1,780 residents in the city between 2010 and 2011. That is a nontrivial gain for a city of 300K people, especially a city that has not grown in so long. But did it happen? Even at the time, you can read my quote in the article questioning what was going on in the data. In short, and I've gone into this in more detail in the past, the gain between 2010 and 2011 was an artifact two things.  One was an error in some group quarters data here in Pittsburgh, specifically a dormitory that was assumed to have been missed in the 2010 census, but actually did close. The second issue was a change in methodology the census used just for that year in estimating subcounty (i.e. municipal) population estimates. The impact of that change I explained more here: Newgeography: Misrepresenting Misoverestimated Population.

Still, the data said the city was growing, a factoid repeated to this day. But it turns out the Census gnomes themselves were not so sure. If you look at the revisions to 2011 data in subsequent data releases you see that the population gain mostly went away in data released the very next year. I’ve put this graph up here before, but here are the various releases of population estimates for the City of Pittsburgh.


You will see that ongoing revisions have modified that early population jump. Note it didn’t go away, and that is pretty historic for the city no matter, but the population gain was only a fraction what was initially reported. Not +1,700 or so, but maybe +400. Small gains did continue into 2012 and 2013 but then population began dropping again. In fact, between 2013 and 2015, the city has pretty much dropped in population by more than was gained in the earlier years. Folk tend to overlook the latter observation. We will see what the latest data brings.



Given that we already know the population estimates for Allegheny County in 2016 shows a significant decline from the year before, it is inevitable that the city of Pittsburgh will show a decline as well. The bigger question as to whether one thinks the population estimates are accurately depicting what is true on the ground is a bigger topic. I’ve gone into problems with building permits data – a key input for these population estimates – in the city of Pittsburgh in the past. But really the very common debate I get into of late is from folks who believe all the housing they have seen constructed in Pittsburgh’s East End of late is indicative of city population growth. I always have to remind everyone that Pittsburgh is a city of 90 neighborhoods and the vast bulk of them are still experiencing much of the same fundamental trends that has caused decline for decades. With just a few exceptions, aging and natural population decline is still ongoing if you move away from the areas of the city dominated by student populations. Now on top of that you also see lower income populations moving out of the city as they are drawn to lower cost housing outside of the city. If you really disbelieve that, cross a river or something and you may get the picture. Anyway.. that is all just preparatory for those who are planning on parsing the next round of data, with population estimates for 2016, which will come on May 25.

3 Comments:

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Wednesday, May 24, 2017 7:56:00 AM  
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