The Wharton School of Business at the University of Pennsylvania in Philadelphia. (Photo by Rusty Kennedy/Associated Press.)

A few weeks ago, a young woman approached me after I gave a talk about my book on finding a job after college. She was in her mid-20s and unemployed despite applying for dozens of jobs and taking on several unpaid internships. “I majored in business marketing,” she told me, “because everyone said it would lead to a job after graduation.”

She’s not alone in that line of thinking. It’s why business is the most-popular major on college campuses these days. The academic fields that make up undergraduate business — finance, accounting, marketing, management, and general business — account for about one out of every five bachelor’s degrees awarded each year.

But not all business majors are created equal in the job market. Research shows that students who major in general business and marketing are more likely to be unemployed or underemployed, meaning they hold jobs that don’t require a college degree. They also earn less than those in more math-focused business majors, such as finance and accounting.

Those gaps exist for all kinds of reasons, but perhaps the most telling is that math-focused business majors tend to work harder while in school than do those pursuing a general business degree. Students majoring in business spend less time studying than anyone else on campus, according to the National Survey of Student Engagement. They also spend less time reading and writing than other majors. One analysis of 10 public four-year universities in Texas found that of the 40 courses needed for a business degree, only one required a writing assignment of 20 or more pages, and only three required assignments of at least 10 pages.

What’s more, the results of national standardized tests, such as the Collegiate Learning Assessment Plus, given to freshmen and seniors, found that students who major in business made significantly fewer gains in college in critical thinking, writing and communication, and analytical reasoning than those who studied mathematics, science, and engineering, as well as the traditional liberal arts (philosophy, history, and literature).

Everywhere I go, parents and students ask me for advice about choosing a major. Here’s what I tell them: Find a major that will challenge you to work hard and spend time on specific tasks, such as writing, reading or math programs, and one that will present you with opportunities to learn from the best professors and be surrounded by peers who will constantly challenge you.

Students today are commonly told they should follow their passions and find a mission in life, but very few 18-year-olds or even 22-year-olds have enough experience in the world to know what truly excites them. Pick a major that interests you, but allow it and external experiences to help shape, not dictate, your mission in life.

While you should consider different majors, and you should keep your options open for a while, don’t think you can do anything you want or have all the time in the world to make a decision. Talent and drive matter to success in most majors. You can’t major in physics if you’re terrible at math.

If money is your goal, Tony Carnevale, the director of Georgetown University’s Center on Education and the Workforce, will tell you that a certain group of majors provide a bigger return on investment over a lifetime. The Georgetown center has found in its research that of the 25 highest-paying majors, all but two (economics and business economics) are in STEM fields.

Even so, Carnevale warns students who pick their majors solely on the basis of the expected paycheck not to count their money too quickly. Salaries for specific majors can differ greatly, too. The top quarter earners who majored in humanities or the liberal arts make more than the bottom quarter of engineering majors. Just 22 percent of graduates with degrees in science and math actually get jobs in those fields and utilize their training.

Another study by the Brookings Institution analyzed the market value of the 25 most commonly cited skills listed by alumni of each college in their LinkedIn profiles. It demonstrated that skill development, not your undergraduate major or the college you choose, is most critical to your earnings potential.

Picking a major is not like buying a new car. You can’t easily test-drive a major, unless you plan to stay in college for many more than four years. A major reflects your interests at one moment in your life. Where you end up in a career is the result of a meandering pathway that most college graduates are destined to take after graduation. Some graduates apply their majors to their careers more than others, and some not at all.

Ask anyone working today if they knew exactly what they wanted to do with their lives at age 18, and they will probably say they had no idea (if they’re being honest). The longer they have been in the workforce, the less likely it is that they are in a career directly related to their college major.

And if you’re majoring in business and think the undergraduate degree doesn’t matter anyway because you’re going to business school, remember this: business students score lowest of all majors on the GMAT, the entrance exam for most MBA programs.