There is one type of internship that’s more beneficial than others

Every year, college students – and even some inhigh school– start freaking out about summer internships.

The short stints in work are often seen as the best way to “boost your hireabilityduring your post-graduation job search,” and a new study has the numbers to prove it.

According to asurvey of students from the Class of 2015by the National Association of Colleges and Employers, students with internship experience were 20% more likely to be offered a job after graduation last year than those without it.

The survey found that 56.5% of students who had had an internship were offered jobs, whereas only 36.5% of everyone else was.

The survey also found that students who had had a paid internship with a private, for-profit company had the highest offer rates – 72% of students had jobs after graduation.

Only 44% of unpaid interns at similar companies were offered jobs.

This discrepancy between paid and unpaid interns persists in other sectors. In the nonprofit sector, paid interns were 10% more likely to be offered a job; for state or local government internships, they were almost 17% more likely; and for federal government internships, they were 12% more likely to have a job.

Paid interns also had a higher median salary once they graduated. Interns who had had a paid internship with a private, for-profit company were offered, perhaps unsurprisingly, the highest starting salary, with a median of $53,521. The median offer for students who took similar, but unpaid, internships was $20,000 less.

Internships have been criticized forcontributing to the widening income inequality gap, and this study seems to reinforce that criticism. Internships have become more and more important for securing jobs after graduation – class of 2011 graduates were only 12.5% more likely to get a job if they had internship experience, either paid or unpaid, compared to last year’s 20% difference.

The opportunities are not equally distributed, however. Lower-income students often can’t afford unpaid internships – they simply don’t have the financial option to forgo a job in favor of experience.