Courtesy of Chris Briem, some very interesting material in this report (it is interesting in general, but also specifically as to Pittsburgh):
http://cityobservatory.org/wp-content/uploads/2015/02/Surging-City-Center-Jobs.pdf
Tables 7 and 13, with accompanying text, are particularly notable. Basically, as in a lot of U.S. cities (outside of places like SF, NYC, and actually Minneapolis), before 2007 employment growth was faster in Pittsburgh's periphery versus the core (the core is defined as within 3 miles of the center of the CBD, and the periphery is everything outside of that, which is actually sort of a conservative measure for Pittsburgh, since here that will miss large portions of the East End such as Squirrel Hill, the Baum-Centre corridor, and Greater East Liberty, but include lots of southern/western lightly-developed and/or mostly residential areas). Since 2007, it has been faster in the core than the periphery.
According to this report, what has been going on is that changing composition of jobs has relatively favored core growth, but before 2007 core areas were nonetheless often at a stark competitive disadvantage in attracting employers. Since 2007 that competitive disadvantage has either greatly reduced (as in Pittsburgh) or actually reversed, which is allowing the ongoing changing composition of jobs (which in fact is even more strongly favoring core areas since 2007) to dominate in favor of core growth.
Obviously if this continues (and there are many reasons to believe it will, including that this is the sort of thing that can actually feed on itself), then it has lots of potential implications for local development--both workplace directly, and residential and retail indirectly. Of course it would be overinterpreting all this to say the periphery is entirely dead--note, for example, that by their measure only about 21% of Pittsburgh employment is core versus 79% periphery, so even slower growth rates in the periphery can add up to decent growth in gross terms. But for those drawing on pre-2007 experience and concluding that all this core area development represents an unsustainable bubble, this sort of study suggests that instead these developers might have a pretty good idea where the action is going to be for quite a while to come.