So to be clear, I have long held there is nothing untoward in any data on the rate at which people, especially young people, are leaving Pittsburgh. What Pittsburgh falls behind in, and has for a long time, is the rate at which people from elsewhere move into the region. That applies to both international immigrants, and domestic migrants moving here from elsewhere in the nation. That by no means implies nobody is coming here, in fact there are sizable flows of people who move into the region each and every year.
Still, there is good news on that front at as well, and it is a more recent phenomenon if anything. For more on that I will just refer to some maps I generated and posted here