The pay gap for men and women just out of college isn't that significant. But the older a woman gets, the wider this gap becomes. 

According to data compiled by Payscale, college-educated women hit their pay glass ceiling at age 39 with an average salary of $60,000, whereas men's pay stops growing at the age of 48 with an average salary of $95,000. 

Payscale says that a lot of this has to do with job choices: "Overall, men and women gravitate toward different careers. The most popular choices for men tend to pay higher than the most popular choices for women."

Also, the survey says that the pay gap begins to diverge around the age of 30, which is "when college-educated women typically starts having children."

At that age, both men and women have increased their wages to around 60 percent compared to their first jobs.  

Salary gap Payscale

PayScale's data included millions of workers, but all of them opted to participate in the survey rather than being randomly selected.