Go to college, get a better job. That’s the message at the heart of the nation’s ongoing efforts to encourage a wider array of students to attain degrees. But college’s effects on graduates’ earnings is complex, varied, and often misunderstood. While a bachelor’s degree clearly matters, where and what a student studies can be just as important as whether the student graduates with a degree at all.

I spoke with Gregory Wolniak, a researcher who’s the co-publisher of a book written once a decade that highlights some of the best research available on the effects college has on students—from earnings and quality of life to affordability and whether students actually learn anything.

According to Wolniak, the director of the Center for Research on Higher Education Outcomes at NYU Steinhardt and the co-author of How College Affects Students, majors matter a lot in determining future earnings, grades matter a lot less, and women have a lot more to gain from earning a bachelor’s than do men.

The interview below was edited for length and clarity.

Mikhail Zinshteyn: Does earning a college degree matter for future earnings?

Gregory Wolniak: There is simply no other substitute for college education in today’s world.

​On average, a worker sees earnings grow 5 percent for every year of college completed within the first few years following college, rising to about 7 to 9 percent decades after college. That’s not even talking about degrees or credentials attained, just per year spent in college. For vocational or associate’s degrees, the earnings benefit compared to just a high-school diploma is roughly 3 to 7 percent. Bachelor’s degree holders make 15 to 27 percent more (than high-school graduates).

Zinshteyn: But what about taking into account the cost of attaining a degree? How does that factor into the equation?

Wolniak: The very best evidence that we have comes from the economists who go to great lengths to take into account all the direct costs, such as tuitions students pay and the fees; and also the indirect costs of attending, like foregone earnings while you’re a student, plus assumptions about how long individuals are likely to work, age of retirement, and taxes paid along the way.

And what they find is that a bachelor’s has a return on investment of 15 to 20 percent. For public-college graduates, the figure is closer to 20 percent. For private colleges graduates, the figure is in the lower end of this range. The difference is because private colleges are more expensive.

Zinshteyn: Do majors matter for earnings over a lifetime?

Wolniak: Majors are the single biggest driver of earnings. Deciding your major plays a bigger role in determining your career earnings than does where you go to school or even deciding whether or not to attend at all. In other words, the average between attending and not attending is less than the differences we see among bachelor’s completers once we compare earnings across fields.

The highest earning majors are in fields such as math, engineering, computer science, information science, and health sciences. The lowest are education and humanities. In the middle you have biology, social sciences, public affairs. Of course, there are other pathways into careers students take across majors. Students majoring in biology are most likely to attend graduate school. So there are differences in earnings down the line. Fields that are rooted in a core competency that are quantitatively based and align with occupations tend to garner the highest earnings.

The difference can be upwards of 40 to 50 percent across majors. It’s not uncommon for engineering majors to make close to 50 percent more than education majors.

Zinshteyn: Do internships matter?

Wolniak: There is very, very little evidence that is generalizable that looks at internships and earnings. The evidence that does exist is that it does make a difference. Internships on average lead to higher earnings—it’s around 4 percent in terms of early career earnings (so five or six years post-bachelor’s). My thoughts are that it’s less about the earnings and more about the employability—internships give students a leg up in securing the job; I don’t know if they impart tangible skills that actually translate to higher earnings. All else equal, yes, do it. If all else is not equal—if you could be spending your time studying and getting higher grades—that will probably benefit you every bit as much, if not more.

Zinshteyn: Do grades matter?

Wolniak: They matter about as much as internships, honestly. So the evidence is somewhat mixed on grades. So if I looked at all the literature that we’ve compiled the past three volumes, we do see, on average, that if someone gets a one-point-higher GPA at graduation they tend to make 5 to 6 percent more in the labor market. The quality of evidence around it isn’t nearly as strong some of the other figures I’m referencing.

Zinshteyn: What else matters in in-school experiences?

Wolniak: Something that is extremely predictive of earnings but can be a blessing and a curse—and in most cases it’s got a far bigger effect on earnings than grades or internships—is whether or not you land a job in a closely related field you studied. Now that can work against you if you’re an education major. But if you are in the sciences or something technical, it’s an added benefit economically.

Zinshteyn: How’s this for a strategy, though: Majoring in what you love but interning in a more lucrative field, like majoring in poetry but interning for a market research firm?

Wolniak: That’s a great strategy, absolutely. But that specific mechanism hasn’t been explored in the literature. It’s a great area for future work. I look forward to actually examining that, because it does make good sense as a plausible way in which internships can compensate for students who study traditionally lower-earning fields.

Zinshteyn: Does the type of institution one attends predict future wages?

Wolniak: The type of college you enroll in does matter quite a bit, but to a lesser extent than what you study. And this is measured by creating an index for institutional quality, which is contentious. If you look at the highest- versus the lowest-ranked schools in the Barron’s Index, for example, we see evidence ranging between a 13 to almost 20 percent earnings difference on average for students in the highest versus lowest categories of the Barron’s Index. We’re looking at high-school diplomas versus bachelor’s, comparing those effects across the highest and the lowest-quality institution (so let’s say I make a $100 more than a high-school graduate and graduated from the lowest-ranked school on Barron’s, the student who graduated from one of the highest-ranked schools on Barron’s will make $113 to $120 more than a high school graduate).

Zinshteyn: Does gender matter?

Wolniak: What we see is that the earnings premium for a bachelor’s degree experienced among women far out-exceeds that which is experienced by men. If we take that 15-to-27-percent earnings effect on a bachelor’s degree on average, if you break that down by gender, we see a significantly higher earnings premium for a bachelor’s versus high-school degree among women compared to men. By some accounts, completing a bachelor’s degree has as much as a 1.5 times larger impact on women’s earnings than it does on men’s. The evidence has been suggesting this for many years.

What might be driving that? When you see averages presented and policy reports that take broad metrics that don’t take into account all the influences that go into shaping peoples life trajectories, we see a different narrative. I’m not saying that women don’t face labor disadvantages, but when we experimentally take into account all the factors that drive the connection between education and work, we see women far exceeding men in terms of the earnings premiums associated with a college degree.

Among different majors there are various wage-premium differences. The sciences and engineering provide a greater wage premium for women; males in social science will see greater wage premium than women.

Zinshteyn: Does race matter?

Wolniak: It’s inconclusive. When I compile the data, it’s all over the place. There’s some evidence that it’s following similar patterns of these gender effects, where earning a bachelor’s brings slightly higher earning premiums for graduates of color than for whites—perhaps this is an outgrowth of an effort to diversify the workplace. That being said, the evidence base is not nearly as strong, and I hesitate to throw much more empirical data out there because of that. The findings tend to differ quite a bit across studies, which suggests we don’t yet know what’s going on.

This article appears courtesy of the Education Writers Association.