Data geek note: The Pittsburgh Economic Quarterly has an article on alternative measures of employment:
https://ucsur.pitt.edu/files/peq/peq_2018-01.pdf
The point I want to focus on is that when you move up to what is called U-6, suddenly Pittsburgh drops significantly below the United States, and way below Pennsylvania.
So what's special about U-6? Compared to all the other measures (U-1 to U-5), U-6 adds in people who are working part-time but want to be working full-time. It is sometimes called an "underemployment" versus "unemployment" measure for this reason.
Accordingly, it looks like Pittsburgh is unusually low in this specific category, meaning relatively few people here looking for full time work have to settle for part time work. You can do the math--it works out to something like 2.8% here, versus 3.4% nationally and 3.5% in Pennsylvania.