We've been on this story for many years, but the Post-Gazette just reported on how even as the population remains flat, the City of Pittsburgh is undergoing rapid demographic change:
http://www.post-gazette.com/local/ci...s/201709140059
The City is rapidly getting younger (driven by a boom in 25 to 34 year olds), more educated, less poor, higher-income, and more diverse in terms of national origin and ethnicity (particularly with respect to Asia). All this explains why there has been robust demand for new apartments in cool areas despite the flat population overall.
Of course the relevant politicians and such immediately pivoted to messages of concern about whether the City will remain inclusive. And they are not wrong to worry! We've seen all this play out in other cities, and it can be a real problem if lower-income people are driven out due to housing becoming unaffordable.
But I hope people understand that at at the end of the day, you can't stop this from happening by trying to block the inflow of these new people--that's what NIMBYs in other cities tried, and it didn't work. Instead, you have to stay ahead of the demand curve with adequate supply, which means approving (without downscaling) lots and lots of residential development.
And then there is transit--we've only got so many areas with good transit service to prime job locations. Higher-income people will gradually take over those areas and crowd out lower-income people, unless we commit to expanding transit service over time. Unfortunately that is largely out of local control and we currently have anti-urban politicians in charge of the state and federal legislatures. But we have to try to change that if we want infrastructure in Pittsburgh (and other similar cities) to keep up with these changes.