Private sector union membership in the U.S. actually rose as a percentage of private employment in 2013 -- slightly. It's still less than 7 percent. Overall union membersip was pretty much flat last year, settling at 14.5 million of a 129.1 million wage and salary workforce.

Looking at Minnesota and Wisconsin, you can see a few things:

- Overall union membership as a percentage of employment (including government workers) is a little higher than the national level in both states.

- Minnesota is more unionized on a percentage and absolute basis, with 362,000 union members that are 14.3 percent of the workforce. Wisconsin has 317,000, and they're 12.3 percent of the workforce.

- Unions have fallen further since the recession in Wisconsin than in Minnesota.

- But Wisconsin's unions made up some ground in 2013. Membership rose there by more than 1 percent, while ticking up just slightly in Minnesota.

- The addition of 17,000 home care workers who are negotiating a contract with the state will increase Minnesota's union share once that's settled.