Protesters shout in front of John Marshall Metropolitan High School in East Garfield Park on the first day of the Chicago Teachers Union strike in 2012. Photo by Jonathan Gibby.

The news: In September, the Chicago Teachers Union called a strike for the first time in 25 years, bringing renewed attention to organized labor in Illinois.

Behind the news: During the past decade, Illinois lost the third highest number of union members in the country, behind Michigan and Ohio, from 1,013,000 in 2001 to 876,000 in 2011, according to the U.S. Bureau of Labor Statistics. But, proportionally, the state’s 13.5 percent drop in union membership ranked in the middle of the pack nationally: 21 out of the 50 states and Washington, D.C.—well behind states such as Louisiana and Tennessee that lost more than 40 percent of union members.

Unionized workers accounted for 16.2 percent of the state’s workforce in 2011, a drop from 18.1 percent in 2001. The 1.9 percentage point drop was slightly above the nationwide median of 1.4 percentage points, ranking as the 18th highest.

Union membership in Illinois has suffered from the migration of traditionally union-heavy industries like manufacturing to other states or overseas, said Monica Bielski Boris, assistant professor at the School of Labor and Employment Relations at the University of Illinois at Urbana-Champaign.

Boris added that the contraction of the state’s heavily unionized public sector has also had an impact on the union membership in Illinois.

“It is true that the public sector has been hurting in Illinois like around the country, but in Illinois … we have serious financial trouble,” she said. “The only state with a worse credit rating is California, and a lot of that has to do with the state not properly funding pension obligations.”