Of 26 states that don't have a right-to-work law in place, Wisconsin had the third-highest percentage drop in union membership between 2010 and 2014.
Wisconsin's union membership has been falling in recent years, even before Wisconsin Republicans passed Act 10 in 2011, limiting the collective bargaining rights for most public sector union workers and requiring yearly recertifications.
In 2014, the state's union membership fell by 11,000 to 306,000, according to figures recently released by the Bureau of Labor Statistics. The data did not distinguish between private and public sector unions.
Union members made up 11.7 percent of the state workforce in 2014, down from 14.2 percent in 2010, the year before Gov. Scott Walker took office.
That's an 18 percent drop in membership percentage between 2010 and 2014. Only West Virginia (28 percent) and New Mexico (23 percent) had bigger losses by percentage in that time among the 26 states without a right-to-work law.
In right-to-work states, employees can't be forced to join or pay dues to unions. Republicans in control of the Wisconsin Legislature have said right-to-work legislation is in the works here, while a group of about 350 private businesses has lined up to oppose it.
Overall, union membership percentages have fallen in the past four years in 37 states and the District of Columbia. Of the 13 states where the percentage went up, nine were states that have right-to-work legislation on the books: Arkansas, Alabama, Florida, Georgia, Kansas, Louisiana, Oklahoma, Tennessee and Virginia.
In Florida, which has had a right-to-work law since 1943, a construction boom has been credited for a slight increase in union membership.
Indiana enacted right to work in 2012 and saw its union membership decline between 2010 and 2014. But the percentage ticket upward toward the end of that cycle, which a legislator chalked up to a lower unemployment rate.
Here's the map showing the change in union membership percentage between 2010 and 2014, where darker red indicates bigger losses and darker green indicates bigger gains.
Change in union membership percentage, 2010-2014
Click on a state for more information.
Source: Bureau of Labor Statistics
Wisconsin has rebounded slightly from its low for union membership in 2012, when it was 11.2 percent, or 293,000 workers.
Here's how Wisconsin union membership has changed since 2000: