The accusations are flying, but there's no definitive answer.
Various studies – mostly by groups with at least some bias – show they make on average either 5 percent more in wages and benefits or between 5 and 7 percent less than private-sector workers with comparable education levels.
The comparison also varies. At higher salary and education levels, public workers are almost always paid less; at the lower end, they may make a bit more.
And, especially for lower-paid workers, unionized ones almost always have a better benefit package than their private-sector counterparts, says Professor Farber.
What role does politics play in the Wisconsin fight?
Walker says it was all about fiscal prudence, but it's hard for most to believe partisan factors weren't at play.
Unions are major political contributors, almost exclusively to Democrats. Unions spent more than $200 million on efforts to get Democrats elected in last year's midterms. One recent analysis by the Wisconsin State Journal found that over the last six election cycles, unions have contributed $7 million in the state, 93 percent of which has gone to Democrats.
"There's no question that the political impact of this would be to sharply reduce the campaign contributions that state unions make overwhelmingly to Democratic candidates," says Franklin. "It would also severely weaken the get-out-the vote efforts that unions are so critical to."
