At the same time, though, unions aren’t the powerhouses they once were. Since the 1950s, when unions had their highest rate of membership, the economy has changed and anti-labor legislation has proliferated. The vast majority of working women—about 90 percent—do not belong to unions. (Nor do the vast majority of men, for that matter.) As a result, for millions of working women today, improving working conditions at the bargaining table—the traditional and arguably most effective way of doing so—is just not an option.

The decline of unions has contributed to a flourishing of labor advocacy groups that are often called either “alt-labor groups” “new actors,” or “worker centers.” Janice Fine, a professor at Rutgers University, has been researching these kinds of organizations since 1992. Back then, there were only five worker centers in the country, she says, and they focused mainly on helping workers understand what rights they already had, and then helping them to make a legal case when those rights were violated, but not obtaining new rights.

But by 2012, the number of worker centers had grown to 214 and expanded their scope. Now, they wage campaigns for pro-labor legislation, experiment with new forms of organization and coalition building, conduct research, and provide resources and education to workers and employers. As they’ve grown, worker centers have become one of the most potent forces for advancing women’s economic interests, such as equal pay, equal protection under the law, and access to family-friendly workplace benefits. It’s no coincidence that many of the most prominent alt-labor groups are run by women.

One of these is the Restaurant Opportunities Center United, or ROC, led by the organization’s co-founder and co-director, Saru Jayaraman. A lawyer, professor, and acclaimed labor organizer, Jayaraman and her colleagues created ROC to support the surviving workers of a restaurant located at the World Trade Center in 2001. Since then, they have won more than $10 million in back wages for restaurant workers, waged successful political campaigns, and built a membership of 18,000 restaurant workers in 15 states.

Data from the Bureau of Labor Statistics show that the restaurant industry is one of the country’s largest and fastest-growing employers, with more than 11 million employees, many of whom depend on tips. According to the National Women’s Law Center, tipped workers face poverty at twice the rate of the rest of the workforce. Two-thirds of that group are women.

In the course of widespread debate about whether to raise the federal minimum wage above $7.25, the fact that there are actually two federal minimum wages is often overlooked. Most workers are supposed to get $7.25 per hour (or more, where states have imposed a higher minimum rate), but tipped workers are promised a base rate of only $2.13 per hour. While employers are required to “top off” their staff’s wages when tips don’t bring their wages up to at least the higher minimum wage, many employers neglect to make up the difference—and they rarely face penalties. This state of affairs is in large part because each time the federal minimum wage has been raised, the National Restaurant Association, one of the nation’s most powerful lobbies, fights hard to keep the minimum wage for tipped workers frozen, arguing that raising the minimum wage would force restaurateurs to reduce hours, lay off staff, or close their doors.