How would you feel if you applied to be CIO and were told, “Oh, sorry, we need a Sagittarius for this position”? That’s how some feel about commonly used personality assessments that human resources departments use in hiring.

The most well-known example is the Myers-Briggs Type Indicator (MBTI), which divides everyone into one of 16 categories based on how they place themselves among four criteria:

Introvert/Extrovert Intuitive/Sensing Thinking/Feeling Perceiving/Judging

After its distribution ownership changed in 1975, the test became more heavily marketed to businesses and more popular, writes Murad Ahmed in the Financial Times. “By 1983, 750,000 people were taking the MBTI annually. In 1993, three million took it.” He estimates that it now earns $20 million per year.

At this point, some 89 of the Fortune 100 companies in the US use it as a human resources tool, writes Melinda Ham in Intheblack, a blog for CPAs. Organizations such as General Motors, Procter & Gamble, and McKinsey & Co. use the MBTI to help manage people, writes Ahmed. Companies such as JDSU say that implementing the MBTI increases job effectiveness for 98 percent of participants, saving the company $20 million.

Proponents of the test suggest that it provides a helpful frame with which to look at colleagues. “It’s 11 o’clock on a Monday night and you’re frustrated with each other and asking, ‘Why are you not seeing it my way?’” one McKinsey employee tells the Financial Times. “Now, you’ve got this thing you can lean back on and understand that the way colleagues see the world is different to how you see the world.”

The test can be particularly helpful in putting together teams, writes Yasmina Blackburn in Huffpost Business. “Understanding the natural tendencies of the individuals on your team can allow for some great predictions,” she writes. “Matching personality types on projects where one person’s strength is another person’s weakness can bring out the best in everyone, allowing people to positively contribute as well as appreciate one another and get along.”

On the other hand, critics point out a number of flaws with the MBTI:

It’s not scientific . While the MBTI was based on the work of Carl Jung, it wasn’t designed by actual psychologists, or even scientists, but by a mother-and-daughter team of writers.

. While the MBTI was based on the work of Carl Jung, it wasn’t designed by actual psychologists, or even scientists, but by a mother-and-daughter team of writers. Definitions are fluid and results aren’t reproducible . “50 per cent of subjects change at least one of their four types when they retake the test,” Ahmed writes. So if you’ve been coding all day, you might come out as “introverted,” compared with a day full of meetings

. “50 per cent of subjects change at least one of their four types when they retake the test,” Ahmed writes. So if you’ve been coding all day, you might come out as “introverted,” compared with a day full of meetings People have to decide which of two extremes to choose —there’s no middle ground. “That a manager may be extroverted at work but a hermit at home isn’t a consideration—nor the idea that he can easily game his test to earn a more desirable result,” writes Alexandra Bosanac in Canadian Business.

—there’s no middle ground. “That a manager may be extroverted at work but a hermit at home isn’t a consideration—nor the idea that he can easily game his test to earn a more desirable result,” writes Alexandra Bosanac in Canadian Business. Everyone is described in positive terms. “Of the 16 possible variations, no type is better than the other and each has unique strengths,” Ahmed writes. “A serial killer might be shown to be methodological, a self-starter and able to put plans into action.” That unrelenting positivity is what’s led some critics to call the MBTI no better than a horoscope.

The biggest problem, of course, is that the MBTI just might not work. “Employees can take results to heart and begin acting to type or defining themselves by a self-limiting label,” writes Bosanac. “For managers, the test might cement pre-existing biases, making them less likely to give employees so-called ‘stretch assignments’ that force staff to work outside their comfort zones.”

For example, former CIA officer Valerie Plame reported that her MBTI score cut her out from certain jobs, and that her coming up as an ENTJ slotted her to be an operations officer. “Different jobs require different traits,” she told the New York Times. “I could never be an intelligence analyst, for example.” Similarly, someone who believes that all IT people have to be introverts might bias them against hiring someone who comes out as an extrovert. (Ahmed points out that the distribution company’s guidelines state: “It is not ethical to use the MBTI instrument for hiring or for deciding job assignments.”)

In fact, some organizations that have implemented personality tests have found themselves on the receiving end of lawsuits. The Equal Employment Opportunity commission is investigating whether personality tests discriminate against people with disabilities, in part by looking into whether the tests discount people with mental illnesses such as depression or bipolar disorder, who happen to be completely qualified for the job, writes Chloe Della Costa in Cheatsheet, a career site.

If the MBTI is so awful, then why is it still so popular, writes Bob Corlett in the Business Journals? Beyond the fact that people love the idea of a test, it’s simple and understandable.

“While there are other psychometric tests, none is as straightforward and easy to administer to assess group dynamics and to gauge employees’ self-awareness,” Ham writes.

Ultimately, the way to take value from the MBTI (as well as DISC, StrengthsFinder, and other alternative personality assessments) is to think of it as descriptive, not prescriptive: Let it open you up to new possibilities, rather than closing you off from options. For example, if a personality test tries to tell you that you should be an actor rather than in IT, look at ways you could bring performance into your job, such as by doing more presentations.

On the other hand, maybe some people are just naturally skeptical. After all, everyone knows Capricorns don’t believe in astrology.

The MBTI and other assessments are only one part of managing talent more effectively. If you’re interested in learning how HR processes can be digitized, check out this free eBook on HR automation.