This article was produced in cooperation with The Hechinger Report, a nonprofit, independent news organization focused on inequality and innovation in education.

It was after caring for her aging mother that Carmen Zapata got the idea of working as a home health aide. Colleges nationwide are offering certificate programs in the field, driven by high demand, and Zapata, who is 60 and lives in the Bronx, found a certificate course at Hostos Community College and enrolled.

“In my desperation to find a job, I was willing to do anything,” she said.

But did she really need the course?

Only about half of home health-aide job advertisements ask for certificates, according to a new analysis of millions of job postings. Zapata’s course was free, but certificate programs for her profession at other schools can cost from $619 online at a for-profit institution to $2,450 at a community college.

All for a job that typically pays less than $11 an hour and for which a certificate program can take as long as a year.

Certificates have become a hot commodity in the higher-education world in recent years, promoted by colleges and by Washington as an important new pathway to a career for people who don’t fit into a four-year degree program. They are the fastest-growing kind of post-high-school credential, with nearly a million a year now being conferred.

The campus of Hostos Community College in The Bronx. Google Maps

Policymakers like them as a way of boosting the proportion of the population that has earned some kind of educational credential after high school. Colleges see them as an increasingly important source of income, particularly at the community college level, and promote them heavily.

Related: The ‘cash cow’ of U.S. universities: Professional certificates instead of degrees

“MTC offers numerous certificate and certification programs to get you started toward a great career—or build your skills within an existing one,” says the website of Midlands Technical College, a two-year public college in Columbia, South Carolina. “At the colleges of DCCCD, you can reinvent yourself in two years or less — with more than 100 majors featuring one- and two-year certificates and degrees to help you build a rewarding career,” says the Dallas County Community College District, in Texas.

Some certificates 'have no currency'

But the new analysis, from the Boston-based research firm Burning Glass Technologies, found that, out of 16 million job openings it reviewed over one year that did not require professional licenses, only eight-tenths of 1 percent, or about 130,000, asked for a certificate.

“There are certificates that people are acquiring that have no currency,” Matt Sigelman, the chief executive of Burning Glass, said bluntly, at the company’s offices overlooking Boston Harbor.

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Another new report, by the public policy think tank Third Way, has found that many graduates of private, for-profit and public technical colleges that primarily confer certificates see little financial benefit from their credentials.

The campus of Midlands Technical College in Columbia, S.C. Google Maps

Earning a certificate “doesn’t necessarily guarantee an adequately good-paying job that allows you to pay down your loans,” said Michael Itzkowitz, senior policy advisor at Third Way and author of the new report. “Often students are leaving without the ability to get a well-paying job and often with unmanageable debt.”

At one in five such institutions, Third Way said, most former students earned less than the average high school graduate, even six years after enrolling. And at nearly four in five, most were unable to start repaying their student loans within three years.

“What we’ve done is use [certificates] as this supposedly quick and nimble way to get people an academic award of some type, but without paying attention to the underlying skills needs of employers,” said Judy Mortrude, director of the Alliance for Quality Career Pathwaysat the Center for Law and Social Policy, or CLASP, an anti-poverty nonprofit group.

Yet another new report, from the American Academy of Arts and Sciences, says that while alternative credentials such as certificates may be appealing, evidence of their effectiveness “is thin and quality assurance is weak.”

Better than high school diplomas

Some advocates for the certificate system find shortcomings in the research. Jobs for which employers value certificates, such as in construction, are seldom advertised in the kinds of online job postings Burning Glass reviews, for instance, said Anthony Carnevale, director of the Georgetown University Center on Education and the Workforce.

And while many of the students in the Third Way study who attended certificate-granting institutions end up earning less than high school grads, said Carnevale, their salaries might have been even lower if they had no certificates.

The Georgetown center calculates that certificate holders earn 20 percent more, on average, than they would with only high school diplomas.

Certificates have other benefits, advocates and skeptics alike agree. “They may have some value as something to put on your resume to say, ‘Well, I may not look like I know about this, but I have a certificate in it,’ ” Sigelman said.

Certificates may also serve as gateways into higher education for students reluctant to pursue associate and bachelor’s degrees, and they can demonstrate job applicants’ initiative in trying to improve their own skills. Nearly two-thirds of students who began their postsecondary educations with certificates went on to enroll in additional college courses, and a quarter earned associate degrees, bachelor’s degrees or both, according to another new report, from the National Student Research Center.

There’s also consensus that, more than 20 years after the federal government started tracking certificates, enormous confusion exists among students and employers alike over what they actually are.

“It’s like the wild west of credentials, with so many things being offered that employers are losing track of them,” said Harry Holzer, former chief economist for the U.S. Department of Labor and now a professor of public policy at Georgetown who focuses on the low-wage labor market.

Defined by the Department of Education as simply “a formal award certifying the satisfactory completion of a postsecondary education program,” certificates vary from vocational to graduate level. They’re awarded for completing anything from one-day seminars to online classes to courses that take several semesters. What they teach can vary among not only different institutions in the same state, but different departments in the same institution. Some come with academic credit that can be cashed in later toward full-scale degrees; others don’t.

Gallagher has found in surveys of employers that certificates are also commonly confused with certifications — credentials issued by industry associations or government regulators, often based on an exam, and which in some professions are required. Several organizations, including CLASP and the American Association of Community Colleges, are trying to bolster the usefulness of certificates by standardizing what they represent so consumers and employers alike have that information.

Related: As Consumers Push Back Against Increased Tuition, Colleges Seek New Revenue

Despite the doubts and confusion, colleges continue to funnel students into certificate programs that have become important sources of revenue. Fifty-four percent of higher education administrators say they see such alternative credential programs as a supplementary source of income, a survey by the University Professional and Continuing Education Association at Pennsylvania State University and the education company Pearson found.

That includes for-profit certificate-granting colleges, which the Third Way study found had the highest proportion of graduates unable to repay their student loans. “There are bad actors in this space that push certificates as the fast way to get a credential, that you see advertised on the bus,” said Mortrude, of CLASP.

Or, as Carnevale put it, “There’s a lot of Trump Universities out there” — a reference to the for-profit real-estate training program that shut down and then paid $25 million to students who alleged it had defrauded them.

Being aware of placement rates and earnings would help students choose the best certificate programs to take. But information about this provided by colleges is often misleading, and the Trump administration — which has delayed the so-called gainful employment rule, an Obama administration effort to determine whether graduates’ incomes justify the costs of academic and vocational programs — has signaled an interest in providing less such information, not more.

“That’s kind of a dumb thing to do,” said Holzer. “Making information available is one of the most cost-effective things government can do. But the Trump administration has not had an enormous respect for data.”

Without having this kind of information readily available to students and employers, “We don’t know the return on this investment,” Gallagher said. “What you get in the end is a really confusing and blurry world where some of the certificates have value and some of them don’t.”

Jon Marcus is the higher education editor of The Hechinger Report. Additional reporting by Matt Krupnick.