Opponents of the "Right-to-Work" rules that Republicans want to bring to Minnesota offered a strong defense this week with a new economic study showing that women and minorities are disproportionately hurt when union dues and membership become optional.

The study, by the Economic Policy Institute in Washington, D.C., found that women and minorities were "disproportionately affected by lower wages and job losses" when union rules were changed.

Let's back up. Just what does right-to-work (RTW) mean?

Currently, Minnesota is not a right-to-work state. That means that union members who work in a unionized company must pay union dues to help offset the costs of collective bargaining.

Republican legislators and even some workers argue that not all workers want to be in a union and that paying dues should be a choice. Republicans argue that union dues are expensive and take money out of the pockets of workers.

Opponents, such as the AFL-CIO, The American Federation of Teachers and the Service Employees International Union (SEIU), argue that union dues are minor and that in exchange, union membership gives workers higher wages and job protections that would not exist but for collective bargaining. Some unions, such as the teachers federation and SEIU, note that many of their locals are comprised of 71 percent women. So a change to the law could hurt dramatically. Other unions such as the United Auto Workers argue that union rules equalized wages for minority auto workers.

Back to the study. Just what did the Economic Policy Institute find?:

* Women's wages dropped 4.4 percent in states where unionized companies made union dues optional. (Men's wages were 1.7 percent lower).

* The hit to wages was higher among non-whites. Blacks and Hispanics were paid 4.8 percent and 4.4 percent less than their non-union peers.

* On average, annual wages and benefits are $1,500 lower in RTW states than for comparable workers in non-RTW states — for both union and nonunion workers.

* Right-to-work laws widened the pay gap between men and women.

The battle at the State Capitol goes on and it is unclear if Republicans have the necessary votes to force a change. Regardless labor organizers say they will lobby hard until the measure dies. Stay tuned. Similar battles have played out in Ohio and Indiana to equally polarizing effect.