We can also see this by looking at changes in college course catalogs. One of the largest and most popular courses in the Stanford computer science department is CS229 — Machine Learning, taught by the artificial intelligence expert and entrepreneur Andrew Ng. This course did not exist in its current form until 2003, when Professor Ng taught it for the first time with 68 students, and very little like it existed anywhere on college campuses 15 years ago. Today, the machine learning courses at Stanford enroll more than a thousand students.

In contrast, much less has changed in my home discipline, economics, where we still mostly offer the classics like intermediate microeconomics or public finance.

Since new technical skills are always in high demand, young college graduates who have them earn a short-run salary premium. Yet when the job changes, these now experienced workers must learn new technical skills to keep up with fresh college graduates and a constant stream of talent from abroad.

The result is slower salary growth and high exit rates from the STEM work force. Between the ages of 25 and 40, the share of STEM majors working in STEM jobs falls from 65 percent to 48 percent. Many of them shift into managerial positions, which pay well but do not always require specialized skills.

Why do the earnings of liberal arts majors catch up? It’s not because poetry suddenly pays the bills. Midcareer salaries are highest in management and business occupations, as well as professions requiring advanced degrees such as law. Liberal arts majors are more likely than STEM graduates to enter those fields.

A traditional liberal arts curriculum includes subjects, like philosophy and literature, that seemingly have little relevance in the modern workplace. Yet many of the skills most desired by employers are also quite abstract.

According to a 2018 survey by the National Association of Colleges and Employers, the three attributes of college graduates that employers considered most important were written communication, problem-solving and the ability to work in a team. Quantitative and technical skills both made the top 10, alongside other “soft” skills like initiative, verbal communication and leadership. In the liberal arts tradition, these skills are built through dialogue between instructors and students, and through close reading and analysis of a broad range of subjects and texts.