First off, it is true that the number and proportion of 20 years olds residing in the city of Pittsburgh went up between 2000 and 2010. It was one of the things that jumped out from the data dump a few months ago. (see tht Trib link, or my post at the time). If you want to look at the broader picture of why the proportion of population is changing making those younger cohorts appear bigger you can go back to what I wrote a decade ago (we’re getting younger every year). Actually that is now over 11.5 years ago. But the city has seen a huge decline in its elderly population which just mathematically makes younger cohorts a bigger piece of the pie. Still there has been a absolute increase in the number of folks in their 20’s residing within the city proper and that is the point worth looking at.
So why the overall increase and how big is it? You can slice the age cohorts a bunch of ways, but let’s go with the groups Citylab used and decade of 20-29 year olds. That age group increased from 60,349 city residents in 2000 to 72,860 in 2010 for an increase of 12,511.
The biggest thing to consder is some other work we have looking at the increasing college enrollment at local institutions… the time series I had there was that between 1996 and 2008 the enrollment at local colleges (region wide mind you) and you get an increase of just under 16K over that period. Parse it and it is about 10K at institutions located within the city proper. The bottom line is that the bump up in 20 year olds in the city of Pittsburgh is mostly if not entirely an increase in the current enrollment at local colleges and universities. Maybe we can parse the enrollment time series to match the 2000-2010 period a bit closer to the decennial cycle in the future, but I am betting the local enrollment increases continued apace or even increased between 2008 and 2010.
We could parse and say some college enrollment is not 20 year olds, but the vast bulk of it is, especially when you consider our large and mostly itinerant graduate student population. Also the enrollment trends I pulled together were just those in 4 year institutions. I bet there has been an increase in itinerant students in other professional education in town over that period which would be in addition to the +16K (regional) number.
There is a bigger corollary out there as well. 20 year olds may be increasing, but long term population trends almost always depend on trends in households with children. So even with more college students adding to the city’s population, the overall city population declined over the last decade. If you look at the children residing in the city you get an overall decline in the population under 18 going down by a remarkable 25% between 2000 and 2010. Few places will ever see growth if you don’t grow, or at lease maintain, households with children and my colleagues Bob and Caesar have put together the definitive neighborhood maps on what is happening with kids in city neighborhoods. There are local neighborhoods with declines in their child populations well beyond the city-wide 25% decline. That is inevitably the biggest driver of future population in most local neighborhoods and municipalities.