Getting shut out of a preferred course can have lasting negative effects on incoming female students, a recent working paper found.

The paper, published by the National Bureau of Economic Research, tracked first-year students at Purdue University who couldn’t take their first-choice classes in 2018 because of a surge in enrollment. Incoming students had to rank their course preferences; 49 percent got into all the courses they wanted, but 51 percent were shut out of a course.

The study found that female students locked out of a course were 7.5 percent less likely to graduate within four years than women who got to take their desired courses. Their cumulative college GPAs were also slightly lower—by 0.05 points—than those of female students who took their preferred classes their first semester. Women locked out of a course were 5 percent less likely to major in STEM fields and even earned about 3.5 percent less in salary after they graduated, compared to female students who took their top-choice courses their first year.

The working paper found no statistically significant effects on male students.

“Our estimates suggest that reducing course shutouts, particularly for STEM courses, can be an effective way to improve female-student outcomes,” co-author Kevin Mumford, an associate dean and professor at Purdue’s Mitch Daniels School of Business, told The Wall Street Journal.