Emily Martin created a state-by-state map of the gender wage gap in the United States. She calculated: Washington, D.C., has the smallest wage gap where women average nearly 90 cents to a man's dollar; Louisiana has the largest gap — women there earn just 65 percent of what men do.

Nationally, women earn an average 79 cents for every dollar men do. The gender wage gap is even wider for black and Hispanic women.

Martin is the vice president and general counsel of the National Women's Law Center. The gender wage gap that she reported is not a new issue. It was President Obama's priority from the start, and the first piece of legislation he signed into law was the Lilly Ledbetter Fair Pay Act in 2009. On the seventh anniversary of the signing last month, he again made headlines by announcing new rules that would require companies to disclose pay data.

But the issue has gone nowhere in Congress.

There are lots of reasons for the gender gap, but Martin says a stubborn, small part is still discrimination.

"There's really disturbing social science studies out there that show that supervisors, male and female alike, without realizing it, will recommend lower salaries for women with equivalent qualifications to men," she says.

Facing pressure from a growing number of activists — who point out that more women than ever are primary breadwinners for their families — states are forging ahead on their own efforts. They have passed a string of equal pay laws in recent years, and more proposals have been introduced in two dozen states so far this year.

A PatchworkOf State Laws

The measures take a variety of approaches. At least five states have banned companies from retaliating if workers talk about their pay and compare notes. Some have made it easier for workers to sue over pay, while others have made it harder for companies to justify paying men more because of a "factor other than sex." Martin says some courts have interpreted that to mean just about anything. A few proposals would bar employers from asking job applicants up front or in an interview about their pay history.

"Because often your pay is set with some reference to how much you made at your last job," Martin says, "the impact of pay discrimination can follow people through their careers."

Another trend is moving beyond equal pay simply for the exact same job title. Nick Rathod heads the State Innovation Exchange, a network of progressive lawmakers. He says a law passed last year in California requires companies to offer similar pay for "substantially similar" jobs, such as a housekeeper and a janitor.

"They'll do worker-based evaluation on things like their skill, their effort, their experience, that type of thing," Rathod says.

Opposition Remains Despite Bipartisan Support

Although it is mostly Democrats proposing these measures, Rathod says an equal pay bill recently passed the Massachusetts Senate unanimously with the support of the local Chamber of Commerce.

"It is a bipartisan issue," he says. "And I think it's hard to be on the side of arguing that mothers and daughters should be paid less than men."

But that doesn't mean there isn't opposition.

"When we look at each one of these bills, I'm not sure if they're accomplishing the end goal," says Loren Furman, chief lobbyist with the Colorado Association of Commerce and Industry. She finds the newly proposed legislation redundant given all the other regulations that are already in place.

"We have a state wage act," she says. "We have an anti-discrimination act. We have the federal NLRB (National Labor Relations) Act."

Furman says companies worry more laws could mean more lawsuits. She says they also worry about a Colorado measure that would ban them from asking job candidates up front about their pay history. Employers tell her they need that to know who is serious about a particular job, and who may be looking for anything they can get.

"The worst thing for an employer is to hire somebody and then lose that person because they ultimately wanted (for example) $100,000," she says.

Whatever laws are enacted, states will be looking to see if they have any impact on a gender wage gap that has hardly budged for a decade.

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