Stereotypes around parenthood are having a lasting effect on the gender pay gap, which has not budged in 20 years, according to a new study by Pew.

Men tend to increase their work hours and receive a bonus when they have children, a phenomenon known as the “fatherhood wage premium.” Women, meanwhile, experience the “motherhood penalty,” which studies have found is closely tied to conscious or subconscious bias against mothers, who may be viewed by employers as less competent or committed to the job.