An old joke in academia gets at the precarious economics of majoring in the humanities.

The scientist asks, “Why does it work?”

The engineer asks, “How does it work?”

The English major asks, “Would you like fries with that?”

But exactly what an English major makes in a lifetime has never been clear, and some defenders of the humanities have said that their students are endowed with “critical thinking” and other skills that could enable them to catch up to other students in earnings.

Turns out, on average, they were wrong.

Over a lifetime, the earnings of workers who have majored in engineering, computer science or business are as much as 50 percent higher than the earnings of those who major in the humanities, the arts, education and psychology, according to an analysis by researchers at Georgetown University’s Center on Education and the Workforce.

“I don’t want to slight Shakespeare,” said Anthony Carnevale, one of the report’s authors. “But this study slights Shakespeare.”

The report is based on previously unreported census data that definitively links college majors to career earnings. Earlier studies have looked at salaries immediately after graduation, but the new report covers earnings across a person’s working life and is based on a much larger survey.

The report comes as the recession and escalating college costs have renewed questions about the value of a college degree. During the past two decades, the average amount of debt a student takes on has roughly doubled in real terms, leading more parents and students to focus on the financial returns of their college investments.

According to the study, the median annual earnings for someone with a bachelor’s degree in engineering was $75,000. The median wage was $47,000 in the humanities, $44,000 in the arts and $42,000 in education or in psychology.

The individual major with the highest median earnings was petroleum engineering, at $120,000, followed by pharmaceutical sciences at $105,000, and math and computer sciences at $98,000.

The lowest earnings median was for those majoring in counseling or psychology, at $29,000, and early childhood education, at $36,000. Workers with a bachelor’s degree in English language and literature, the most popular major within the humanities, have median earnings of $48,000.

These figures do not include workers who went on to complete advanced degrees, and the study does not investigate the value of such degrees.

In general, the study found that a college degree is a good investment. It showed that a worker with a bachelor’s degree can expect to make 84 percent more in a lifetime than a colleague who has only a high school diploma.

“Education is so off-the-charts expensive now,” said poet and Florida International University professor Campbell McGrath. who noted that his son is considering an anthropology degree. “You are making a really weird decision if you decide to send your kids off to study philosophy. It would be a better world if we all studied the humanities. But it’s not a good dollars-and-cents decision.”

A practical matter

For more than a century, debates have erupted over the real-world value of the humanities. As far back as 1891, Andrew Carnegie, the self-made millionaire, was taking aim at the less practical.

“In the storms of life,” he asked during a commencement speech at a business and shorthand college in Philadelphia, are graduates “to be strengthened and sustained and held to their post and to the performance of duty by drawing on Hebrew or Greek barbarians as models? . . . I rejoice, therefore, to know that your time has not been wasted upon dead languages, but has been fully occupied in obtaining a knowledge of shorthand and typewriting.”

Today, in an era of shrinking budgets, high unemployment and international competition, the debate has taken on heightened interest.

“As the economic downturn has continued, there has been more of a focus on return on investment from college,” said Mark Kantrowitz, publisher of Finaid.org, which offers financial advice to students. “Even in 17-year-olds, we’re seeing emphasis on maximizing returns on investment — that is, getting trained in areas that pay better.”

Job creation

Earlier this year, Microsoft founder Bill Gates, who through the Bill and Melinda Gates Foundation has become a force in education debates, weighed in on the side of aiding college departments based in part on what jobs might be created from them.

“It’s actually very interesting when you take higher ed and think of it in that way, the amount of subsidization is not that well-correlated to the areas that actually create jobs in the state — that create income for the state,” he told a meeting of the National Governors Association earlier this year.

The Center on Education and the Workforce has been funded in part by the Gates Foundation.

But others, many of them in academia, warn against relying too much on averages.

“These types of correlations are a little bit dangerous,” said David Oxtoby, president of Pomona College. “There are lots of individual cases, and everyone is different. . . . Parents should be very careful about pushing their kids in directions that are not right for them.”

Oxtoby noted that a person who majors in English might be less interested in making a lot of money and that the disparate salaries might reflect the preferences of an individual rather than the value of a major.

Others said that the American ideal of a “liberal education” — one that offers a broad knowledge of science, cultures and society and high-level analytical and communication skills — is being copied internationally.

A quality liberal education “is the most powerful form of learning we offer in this country, and even today, Asian universities and Middle Eastern leaders are trying to import it,” Carol Schneider, president of the Association of American Colleges and Universities, said by e-mail. “The major itself (whatever it is) is only a part of a strong liberal education.”

But with college debt weighing heavily on students, Carnevale said it’s important to know how the job market considers what’s valuable.

“The engineering major makes more money because he or she is more productive. In the end, the market is very discriminating,” Carnevale said. “There’s this business about people in college following a dream. But how do you know it’s a dream? Students have a right to know what kind of career they’re headed for.”