Female chief executive officers receive higher base salaries than male chief executive officers, but factor in bonuses, perks, and stock-based compensation, and female CEOs have a total compensation that is only 85 percent of their male counterparts', according to a study by the Corporate Library.

While the study found that female CEOs were paid 103 percent of median male CEO base salary, the median total compensation (bonuses, stock-based compensation, etc) for female CEOs is $1,746,000, compared with $2,049,000 male for CEOs.

The differential worsens for female CEOs of the largest companies, the study found. At these companies, female CEOs' earning power is less than two thirds of their male counterparts.

The study's authors said they made adjustments for company size, performance, and industry but found that none of these influences could fully explain the differential. However, the low number of female CEOs means a small sample size, so that could have affected the figures.

“Perhaps it is the number of female CEOs,” says Paul Hodgson, co-author of the report. “Less than 3 percent of CEOs were women, so there were nearly 33 times as many male CEOs as there were female CEOs. This is a shockingly low number in any major Western economy, but the small number of women in the sample--only 80--–may be affecting the findings.”

The survey, examined compensation data in 3,242 U.S. and Canadian companies. Find out more about the study at www.thecorporatelibrary.com.