We have lacked reliable numbers about the effect of Act 10 on union membership in Wisconsin, but the Wall Street Journal took a stab at it this morning, reporting that AFSCME lost more than half its members in a year. As for teachers’ unions:

In the nearly 15 months since Mr. Walker signed the law, 6,000 of the AFT’s Wisconsin 17,000 members quit, the union said. It blamed the drop on the law.

No one is passing around definitive numbers for the Wisconsin Education Association Council, but we do know the union laid off 42 staffers last August, which strongly suggests a membership loss in line with AFT Wisconsin’s numbers.