the easy part
I hate to say that was all the easy part. The harder part is dealing with continuing ridership declines. Other than a brief tick up corresponding to the hysteria surrounding the rapid increase in gas and energy prices a few years ago, the overall trend in Port Authority ridership has reverted back to its long term downward trend. Over last 3 years annual decline is averaging over 2%/year. Note that Allegheny County population change over that time is nearly flat, though that is from census estimates. We will obviously get new decennial census population counts in the spring. So that trend likely represents continuing change in mode among commuters more than anything else, though that is a study worth doing.
This is what I see for the Port Authority ridership trend. :
Which when you add in the fact that Downtown and Oakland employment levels are strong you have to wonder how everyone is getting to work. (yes, all policy issues in this town are connected, though we keep debating them piecemeal over and over again.) Then you realize why parking downtown remains quite full. Add in greater enrollment at local colleges and universities and I suspect a growing spatial concentration in services such as for hospitals and you really must get a greater potential demand for transit services year over year. Still fewer and fewer on the bus (or T.. .though T ridership is steadier than bus ridership).
Note I just picked April to plot because I wanted to compare a particular month to be clear and free of seasonal issues There is data out through June, but I didn't want to use a summer month since one could argue that isn't fair to the Port Authority because of all the students that make up its ridership through the year. So I picked April as the most recent month I wanted to compare. Other than that the month is arbitrary and I think I will have to come back to this when data from the fall is out.