Fewer students are going to college this fall, as enrollment in higher education has fallen for five straight years, according to the National Student Clearinghouse, which tracks enrollment. Some 2.4 million fewer students are enrolled than at the recent peak in 2011.

Several factors are to blame for declining enrollments. For one, there are fewer students graduating from American high schools these days compared to just a few years ago as the teenage population has dropped off in much of the country. Second, because of the strong economy, adults who might consider going back to school to sharpen their skills are opting to stay in their jobs.

But a third factor that is rarely discussed is also at play: the rise of alternative types of higher-education credentials in an age when we always need to be learning.

The assumption about the college-for-all movement over the last few decades has been that everyone needs a four-year degree rather than everyone needs further education after high school. As a result, the bachelor’s degree has become the new high-school diploma, at least in economic terms. A study published earlier this year by the National Bureau of Economic Research found that while the wage premium of the bachelor’s degree grew rapidly in the 1980s, its growth slowed in the 1990s, and has largely remained unchanged since 2010. The reason? Technology.

In all industries, automation has begun to supplant jobs held by workers with four-year degrees. So workers with a bachelor’s degree are forced into lower-skill jobs with lower wages. Rather than a ticket to a high-paying, managerial job, the four-year degree is now the minimum qualification to get in the door to any job, thus requiring additional credentials to advance in a career.

“The historic relationship between higher education and the job market is changing, and colleges don’t yet realize it.” said Ryan Craig, author of “College Disrupted: The Great Unbundling of Higher Education.”

The college diploma hasn’t always been the primary qualification to enter the job market that it is now. For much of its history, higher education had a tortured relationship with awarding any type of credential — whether certificates or degrees —although they became the foundation of the business model for colleges. “There is little consensus about why employers assign jobs on the basis of the educational credentials of job candidates,” David Bills, a professor at the University of Iowa, wrote in a study of credentialism.

When Harvard University opened in 1636, the credential didn’t even matter. There were no courses, and the curriculum was derived from the classic liberal arts. The Industrial Revolution forced colleges to rethink their curriculum from solely focusing on the liberal arts to incorporating the practical arts to serve the growing legions of factories, railroads and mechanized farms. In 1851, Harvard awarded the first bachelor of science degree, and in the following two decades, another two dozen institutions would follow. Still, the B.A. degree was seen as superior. Harvard, for instance, had lower admissions standards for science students, and the length of their degree was three years instead of the normal four. (How times have changed as the B.S. degree has risen in popularity with students interested in pursuing “practical” majors to get jobs.)

The current flattening of the economic value of the bachelor’s degree should not be interpreted as discouraging anyone from going to college. Indeed, the changing nature of work, with the skills needed to succeed on the job quickly evolving, indicates we will need more education, not less, in the future. But just like during the Industrial Revolution when new processes required new disciplines and degrees in engineering and science, the digital revolution of today again requires a makeover for our historical vision of the college degree.

That transformation is already underway. Several universities, including the Massachusetts Institute of Technology, the University of Pennsylvania and Boston University, have launched MicroMasters degrees through edX, an online learning provider. Under the program, anyone can take a suite of courses across a range of more than three dozen programs, including supply-chain management, entrepreneurship, and solar-energy engineering. Those who do well and pass a set of proctored exams can earn a MicroMasters, equal to somewhere between a quarter and a half of the course material of a typical master’s degree.

The MicroMasters also has lower tuition. At MIT, for instance, the on-campus master’s degree in supply-chain management costs nearly $70,000. The MicroMasters is just $1,350. When edX started the degrees with MIT, officials projected they would enroll 200,000 students across all programs; within the first nine months, more than 1.3 million people signed up.

Georgia Tech has also been inundated with students for its online master’s in computer science. Within three weeks of announcing the program in 2014, the school had more than 2,300 applicants, about twice as many as it typically receives for its on-campus master’s. By spring 2017, nearly 5,000 students were enrolled. Tuition for the program is about $6,600, compared to $40,000 for an on-campus degree. Now, Georgia Tech is expanding the range of the program, and this fall started offering an online master’s degree in analytics for less than $10,000.

Such microdegree programs appeal to students who don’t need all the courses required by traditional graduate programs, or can’t afford the time or price of legacy degrees. So the drop in enrollment at colleges nationwide can’t simply be blamed on fewer students in the pipeline. The demand for alternative types of credentials suggests another reason: Colleges might not be offering what students want and what today’s workforce needs as entire occupations expand and contract at an alarming pace.