The conditions that create the pay gap between men and women may start before they even enter the workforce.
According to the economics research team at Glassdoor, male and female college graduates who hold the same degree will "self-sort" into different occupations due to societal pressure and norms. Male graduates will gravitate toward high-earning jobs, whereas women will gravitate towards lower-earning jobs.
For example, a male graduate with a biology degree is more likely to gravitate towards higher-paid jobs such as data analyst or manager, while a female graduate with the same degree is more likely to gravitate towards lower-paid jobs such as a sales associate or lab technician.
The process of self-sorting is one of several factors that contribute to this stark economic reality: The average male worker will earn $430,000 more than his female counterpart over the course of a 40-year career, according to the National Women's Law Center, a nonprofit advocacy group.
Why do college graduates gravitate toward particular occupations? Social pressure, says Glassdoor's Chief Economist Andrew Chamberlain.
"There are roles in the labor market that Americans have become accustomed to thinking of as 'men's' or 'women's' jobs," he says. "These perceptions affect which jobs men and women feel comfortable moving into."
The fact that many high-paying industries like engineering or computer science are male-dominated may also discourage women in subtle ways.
"Women often face social stigma for working in traditionally male-dominated jobs," he says, "and that's likely part of the explanation for why we're seeing this pattern."
Taking 46,900 anonymous, user-submitted salary and education data reports, Glassdoor researchers analyzed how much male and female professionals with the same college degree made. Focusing on the 50 most common majors, researchers found an average 11.5 percent pay gap between men and women in the first five years of their careers.
Here are 15 college majors where the gap in pay after graduation is most pronounced: