Neither conservatives nor liberals disagree that these unions raise wages and employment for their members (i.e., firefighters, teachers and police). But research I recently completed finds a solid empirical relationship between public sector unions’ concentration and the size and cost of state government, suggesting that what’s good for the public sector employee goose might not be good for the taxpayer gander.

Over the last three decades, union membership in the private sector has fallen precipitously, from 24.2% in 1973 to just under 7% in 2011. Over the same period, public sector union membership jumped by 14 points, from 23% to 37%…

The stability of public sector employment is reflected in Bureau of Labor Statistics job tenure data, which find that median tenure for a government employee is anywhere from 37% to 97% higher than in the private sector. And recent research published in the Journal of Economic Perspectives concluded that the salary and benefits of state and local government employees is as much as 21% higher than of private sector employees doing similar work.