Last Friday was Decision Day, the deadline for high school seniors to finally make a choice about where they’re going to college in the fall. In the coming months, seniors and their parents inevitably will be asked many times which school they picked. That question is usually followed by this one: What’s your major going to be?

Even in today’s fast-moving economy, where industries expand and contract at an alarming pace, students are still asked to select a major at 18. It’s irrational. Most college freshmen really have no idea what they want to do, even if they declare a major before they arrive on campus.

That’s why a quarter of freshmen change their major by the end of their first year of college and another half say they plan to. Or students hedge their bets by picking two majors, one they like and one they think might lead to a job and a big paycheck. At some elite schools, the ranks of double majors now make up 30 percent to 40 percent of graduates.

Unfortunately, given the rising price of college, too many decisions about majors these days are driven by the expected return on investment after graduation. Lifetime earnings between bachelor degree recipients can vary greatly depending on major. Graduates with the highest-paying major (petroleum engineering) earn $3.4 million more than the those with the lowest-paying major (early childhood education) during the course of a career, according to a study released Thursday by Georgetown University’s Center on Education and the Workforce.

The study, which analyzed wages for 137 college majors, found that of the 25 highest-paying majors, all but two (economics and business economics) were in the STEM fields (science, technology, engineering and math). No wonder nearly half of college graduates major in either business or STEM fields, and four out of five students today major in a “career-focused” field.

Even so, Tony Carnevale, the director of the Georgetown center and one of the authors of the study, warns students who pick their majors solely on the basis of the expected paycheck not to count their money too quickly. Salaries differ greatly within majors, too. He notes, for example, that the top quarter earners who majored in humanities or the liberal arts make more than the bottom quarter of engineering majors.

If freshmen see majors as fungible anyway, students should be encouraged to explore their options in their first year of college to see what actually interests them. There’s no need to rush the decision, like we do so much of the first two decades of life.

But that’s exactly what happens too often in college as academic advisers pressure freshmen to pick a major so that they can complete the courses needed to graduate on time, especially as some schools stuff more requirements into their majors.

Many students believe that picking a major is tantamount to choosing a career for life. It’s not.

I was reminded of that a few weeks ago when I attended the Major Declaration Dinner at Franklin & Marshall College, a small liberal arts school in Lancaster, Pa. Students at F&M don’t need to officially declare a major until the end of their sophomore year. At the annual dinner, students sit at tables by their newly declared major, with faculty members in that department and alumni who graduated with the degree.

At the philosophy table, I sat next to Katelyn Greller. She told me that her choice of a major often elicits questions from adults who wonder what she’s going to do with the degree. “I don’t know yet,” she said. “But it will give me a good foundation in reading, writing, and critical thinking and that will prove useful in many fields.”

Nearby Richard Bidgood, who graduated from F&M in 1976 with a philosophy degree, agreed. He recently retired from banking, a field that tends to attract mostly finance, business, and economics majors. He said his colleagues appreciated his philosophy background. “It helped me think through problems when we were making deals and ask the right questions,” he said.

F&M’s president, Dan Porterfield, told the students that choosing a major is a “statement of interest, value, and identity.” He reminded them that some of the college’s most successful alumni majored in something unrelated to their current career field. Mary Shapiro, former chair of the U.S. Securities and Exchange Commission, received her degree in anthropology. Richard Plepler, president of HBO, majored in government.

As I research my next book about the transition from college to the workforce, I’ve been asking employers what they most want when they recruit those with newly minted bachelor’s degrees. They hardly ever tell me that they care about a job applicant’s major.

Tim Brown, the CEO and president of IDEO, the influential design firm, said in an interview that the only time he considers a major is when the applicant has a creative combination, such as history and architecture, that can be useful to the company which receives 20,000 applications annually for about 150 openings. “We’re looking for a specific skill set that doesn’t come from any particular major,” Brown said.

Colleges like majors because it’s an efficient way to organize their faculty members by departments. But that doesn’t mean we need to organize students in the same way. A design exercise last year at Stanford University suggested that instead of majors, students should declare a “mission” to help them find meaning and purpose behind their studies.

Majors are probably not going away, but at the very least we shouldn’t be asking 18-year-olds to make a decision about what they want to do for the rest of their lives before they even step foot on campus for their first class.