Thanks to Sheryl Sandberg’s new book and non-profit organization aimed at improving professional employment and advancement opportunities for women, the term “lean in” has become known nationwide as a term for women (and men) in the workplace who prioritize career advancement in their lives and push for what they feel they deserve. Increased media attention has fallen on the debate of whether men and women are truly given equal opportunity to advance in the workplace. Recent studies and events reveal how complex the issue of gender equality in the workplace truly is.

The persistent gender wage gap

According to the Families and Work Institute’s National Study of the Changing Workforce, women have made strides in closing the gender wage gap in America. In 1979, the average full-time female worker’s weekly earnings were a mere 62 percent of what the average male employee earned; by 2007, the average woman working full-time earned a weekly wage that was about 80 percent of what her male peers earned. Since then, numerous other studies have shown that the wage gap has hovered around 20 percent or more. For example, according to the United States Census Bureau, working women’s full-time, year-round earnings between 2011 and 2012 were 23 percent lower than the annual earnings of full-time male employees during the same time period. Furthermore, this 23 percent disparity does not even take into account the abundant instances in which ambitious, proactive women are not paid for their work.

According to The Atlantic, a 2009 study by InternBridge revealed that women hold up to 77 percent of all unpaid internships at non-profit organizations, government institutions and private companies. This fact and its implications were thrown into the spotlight when a staff member at — a non-profit organization that Sheryl Sandberg created specifically to further the career interests and advancement opportunities of professional women — posted on Facebook that she was looking for unpaid interns. Social media and traditional publications promptly erupted with criticisms. The Atlantic reported that one man posted on Lean In’s Facebook page: “Lean in is a global community committed to offering women the encouragement and support to lean into their ambitions, as long as those ambitions don’t include paid work.” In other words, unpaid internships such as the ones advertised, and the fact that significantly more women than men are in these unpaid roles, show that women are indeed leaning in — pursuing their professional goals and gaining work experience — yet are once again getting financially shortchanged for their efforts.

The gender wage gap and findings like those from InternBridge are especially concerning, given the fact that women are more active in the workplace than they have ever been. According to a Pew Research Center study released in May of 2013, working mothers are the sole income providers in an unprecedented 40 percent of American households with children under 18. In addition, the National Study of the Changing Workforce found that women’s overall labor participation rate has increased from 42 percent to 57 percent between 1950 and 2007, while men’s labor participation rate during that period has actually decreased substantially, from 82 percent to 66 percent.

Women’s career ambitions have also increased to match those of men, with 65 percent of women under 29 declaring that they wished to have jobs with more responsibility in 2008, a percentage that is only 3 points lower than the 68 percent of men who desire more responsibility on the job. In short, women’s engagement in the workplace is at its peak, and yet, according to Catalyst, women comprise only 4.2 percent of the Fortune 500 list of CEOs, and as discussed previously earn only 77 cents for every dollar that men earn.

Women’s choices versus societal stereotypes

Theories abound about why the gender wage gap still persists, and include social biases, the industries women tend to enter, and even working women’s own evaluations of what they deserve. For example, Forbes cites American Express OPEN’s finding that even when female CEOs write their own paychecks, they pay themselves 24 percent less than their male counterparts. In addition, according to NPR, men are approximately four times more likely to ask for a raise than women are. Furthermore, Phil Gardner, who directs Michigan State University’s college Employment Research Institute, partially explained the prevalence of women taking on unpaid internships in The Atlantic by noting that many women select college majors and careers in education, health care, social justice and non-profits. “That’s where the unpaid are,” he explained.

Yet, as Megan Casserly points out in her article for Forbes, it is also inaccurate to attribute all of the gender wage gap on women’s decisions in the workplace. “I’ve grown tired of placing the burden of blame so solidly on women. That we must network more, negotiate more aggressively, find a sponsor and a mentor while doing our jobs harder better and faster than our male colleagues,” she writes. “I don’t believe pointing fingers at ourselves is getting women anywhere.”

As multiple causes contribute to this issue, the solution will likewise involve a multifaceted approach that tackles not only the view of women in the workplace, but also women’s views of themselves, policies of salary equality and/or transparency, and pay disparities across various industries.