A new study from Cornell University found that mothers were penalized in the hiring process compared to childless women and men. Researchers set up a mock company and had male and female students evaluate applications for a marketing position. With all qualifications being equal, the evaluators said they would hire 84 percent of the women without children, but only 47 percent of the mothers. Additionally, the study found that mothers were offered lower salaries than women without children, with a salary gap as much as $11,000 in starting wages.

Both male and female evaluators were equally biased against women with children, which was surprising to the researchers since many of the students grew up with working mothers themselves.

In addition to the motherhood penalty, the study discovered a fatherhood bonus since evaluators assumed "breadwinning" fathers would be more dedicated to their jobs than men without children. Researchers say the study reinforces the "glass ceiling" barrier that prevents women, particularly mothers, from advancing to top-ranking positions.