Cities are finally banning employers from asking everyone's least-favorite interview question

Even the most casual, free-flowing job interview can take a sour turn if the hiring manager asks one question.

What's your current salary?

In the best case, the question can promote fruitful negotiation. In the worst case, experts say it can perpetuate a deep-seated gender wage gap.

On April 5, New York City became the latest in a string of cities to pass laws banning employers from asking how much potential hires make. It follows similar measures in Philadelphia and New Orleans, along with more sweeping legislation in Puerto Rico and Massachusetts, designed to eliminate salary history from the interview process.

The gender wage gap has fallen significantly in the US over the last couple decades, but data indicate women still make 83% of what men make, on average. Pew research has found gaps often persist due to women taking breaks in their career to raise a family - a factor that advocates point to as a flaw in the American approach to work-life balance, namely parental leave.

Massachusetts became the first US state to pass a salary history law back in August of 2016. In an effort to give businesses time to amend their hiring practices, the rule will require companies to state salary and other pay figures numbers up front, starting in 2018.

Sarah Fleisch Fink, director of workplace policy and senior counsel at the National Partnership for Women & Families, says the bans are an important step in the ongoing fight for equal pay.

"If somebody has faced gender-based pay discrimination over the course of a career or just in one prior job, and a new employer uses salary history to set pay, essentially you continue to carry forward that gender discrimination from job to job," she tells Business Insider.

One thing the laws don't cover is interviewees volunteering their current salaries on their own. In that respect, men may still wield an advantage, says Claudia Goldin, a Harvard economist who studies gender inequality.

"There are no barriers to stating that you make X amount of money and would not work for less that amount," Goldin says. For instance, research has shown men tend to negotiate far more often for a higher salary than women do. A salary history law has no bearing on that aspect of the hiring process.

"Thus, if women disproportionately do not state what they make relative to men," Goldin says, "how does the regulation help them?"

Fink concedes a similar point - specifically, that employers still bear enormous responsibility in ensuring they pay men and women equally, given both sexes take different approaches to securing a new job.

The biggest step, she says, is taking a hard look at their own payroll to check for any wage gaps.

"Public-policy solutions are definitely a piece of it, but there are certainly steps employers can take, and that's a big one," she says.