They are among the highest taxed and most regulated states, and these policies are what drive state economic growth. Pennsylvania, with a mediocre to poor tax and business climate, is also a high outbound state, but residents are going to high-growth, low tax states like Virginia, Texas and Florida.
Southeastern PA is a microcosm of this phenomenon, as Philadelphia (with the 2nd highest local tax burden in the US) is losing residents, who are fleeing to the suburbs, which many observers have noted are becoming more liberal.
In fact, it would seem that liberal’s support for a greater role for government in the economy and more spending is driving up taxes and regulation–which results in liberals fleeing (following conservatives) those states and cities, only to support similar policies elsewhere.
It should also be noted that while PA may be becoming more “liberal” based on these trends, we are also losing influence nationally, as we are likely to lose one or two more Congressional seats and electoral votes in 2012.