New low for Unionization Rate in Pittsburgh
I'd point out two things. The annual time series compiled from the CPS shows more variation than you would expect in the real world, and that is to be expected from survey data. But if you smooth the trend out to remove the sample error you clearly see the downward trend. I'd suspect the actual rate for 2015 to be more like 8%, which still is pretty much an all time low, and something below that now in 2016.
But the bigger question that comes up when I talk about this data is what exactly is being measured. Private sector unionization here measures union membership, but only among those currently employed. So when you look at the greater obvious union presence at the Labor Day parade for example, realize that here in Pittsburgh for sure there are a lot of households with retirees or former union workers as well that would not be captured in this stat. Note also the overall unionization rate in Pittsburgh is just a little big higher because public sector jobs have a higher unionization rate here.
A couple thoughts on what it means. Whenever you hear of someone saying - and they still occasionally do - that somehow unionization impedes economic growth in Pittsburgh... the unionization here is actually below that of a lot of other metro areas. Seattle for one example now show a private sector unionization rate of 10.0% in Seattle, compared to Pittsburgh at 6.8%. Seattle has been doing pretty well nonetheless.
Also, the historical trend is still a big deal. This time series only goes back to 1986, but even then the private sector unionization rate in Pittsburgh was measured at 18.8% - or about 3 times the current rate. 1986 was clearly after so many union jobs went away across Western Pennsylvania. Remember this metric measures unionization only among those currently employed. So the rate was much higher just a few years before that. But go back further. My research tells me that peak manufacturing employment came in the early 1950s when manufacturing jobs alone represented 40% of the local workforce. Any measure of unionization back then was far upwards of that 40%.