CEO gender gap is still huge, and getting worse

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The most unequal developed nation is...

Gender equality is still a long way from the executive suites of corporate America.

The nation's largest companies remain laggards in terms of getting women into CEO positions, according to a new study that shows S&P 500 company leadership remaining the domain of men, with almost no gains over the past nine years.

In fact, 2015 saw regression, with the total number of female CEOs dropping from 25 in 2014 to 21 as 2015 comes to a close, according to the study from Pavle Sabic, director of market development at S&P Capital IQ.

"Despite all of the attention placed on increasing the number of female executives at American companies, the needle on the gender gap has hardly moved," Sabic said in a narrative accompanying the study. "The gender gap at the CEO level of S&P 500 companies is not closing. Growth rate for new female CEOs is only one per every two years."

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The decline in female top executives comes even amid evidence that they generally outperform their male counterparts.

A study early this year from Bespoke Investment Group found that share performance at companies led by female CEOs had been topping male-run companies by 5 percentage points. In 2015 as a whole, female-led companies are averaging returns of 0.19 percent, compared to the index price decline of nearly 2 percent.

The chart below shows the top- and lowest-performing female CEOs this year: