In which national newspaper did the following appear (not on the opinion pages):
But public workers have a unique relationship with elected officials, because government employees are effectively negotiating with bosses whom they can campaign to vote out of office if they don’t get what they want. Private unions, in contrast, don’t usually have the power to fire their members’ employers.
The answer is here.
In her review of the literature on public sector unions, Eileen reaches much the same conclusion. She writes:
In addition, however, public sector unions are also able to increase demand for their labor through the political, legislative, or regulatory process, thus increasing wages further than private sector unions are able to.