How many months make a trend?
This is not meant to confuse. The metric here is Pennsylvania employment in Mining and Logging industries minus similar data for the Pittsburgh region. Basically what is happening across Pennsylvania with the exception of Pittsburgh. This is also graphing out the net change in jobs for each month compared to the same month in the previous year.
The Pittsburgh time series does not go as far back in time as the statewide data. But looking at statewide data for Pennsylvania tells another story. If you look at month over month employment change in mining and logging, the April data is showing the largest one-month drop in almost 20 years. Maybe it is all a temporary aberration?