Most of psychology hasn’t ever seen Myers-Briggs test—the one that labels people with mysterious sets of letters like ESTJ, INFP, INTJ— as a good way to learn about people. But companies seem to have missed the boat on that. According to The Guardian, they rely on those four letters far more than they should.

Polling their readers, The Guardian uncovered many reports of companies using Myers-Briggs (MBTI, for short) in all sorts of ways. Some companies put it on their employees profiles. Others use the test for team-building. Some even use it during the interview process.

For those who preach the MBTI, this is a quite lucrative business. The Guardian says:

Training in the MBTI and its variations is typical for those in Human Resources etc. and can be quite expensive. The MBTI as an industry apparently makes $20 million a year. When you’ve spent so much time and money on learning something, of course you’re going to have a faith in it, even to the point of cognitive dissonance.

But as for accuracy and helpfulness, well, the MBTI fails that test. Here’s The Guardian again on just some of the weaknesses:

he most obvious flaw is that the MBTI seems to rely exclusively on binary choices….For example, in the category of extrovert v introvert, you’re either one or the other; there is no middle ground. People don’t work this way, no normal person is either 100% extrovert or 100% introvert, just as people’s political views aren’t purely “communist” or “fascist”. Many who use the MBTI claim otherwise, despite the fact that Jung himself disagreed with this and statistical analysis reveals even data produced by the test shows a normal distribution rather than bimodal, refuting the either/or claims of the MBTI.

Skeptoid explains a bit about how such an unscientific concept could become so popular. For instance, it fools you in many of the same ways that zodiac signs do:

One obvious trait that the MBTI has in common with horoscopes is its tendency to describe each personality type using only positive words. Horoscopes are so popular, in part, because they virtually always tell people just what they want to hear, using phrases that most people generally like to believe are true, like “You have a lot of unused potential.” They’re also popular because they are presented as being personalized based on the person’s sign. This has been called the Forer Effect, after psychologist Bertram Forer who, in 1948, gave a personality test to his students and then gave each one a supposedly personalized analysis. The impressed students gave the analyses an average accuracy rating of 85%, and only then did Forer reveal that each had received an identical, generic report. Belief that a report is customized for us tends to improve our perception of the report’s accuracy.

Scientists who have tried to validate the test have come up short. One researcher at Indiana University tried to take a rigorous look at the MBTI in comparison to other psychological methods. His conclusion:

In summary, it appears that the MBTI does not conform to many of the basic standards expected of psychological tests. Many very specific predictions about the MBTI have not been confirmed or have been proved wrong. There is no obvious evidence that there are 16 unique categories in which all people can be placed. There is no evidence that scores generated by the MBTI reflect the stable and unchanging personality traits that are claimed to be measured. Finally, there is no evidence that the MBTI measures anything of value.

Ouch. Now, it’s not really that surprising that bosses use things that aren’t proven to work. Things like encouraging multi-tasking. But at The Guardian, Dean Burnett was surprised at just how common the MBTI seemed to be. Here’s his theory about why:

I personally feel it’s more to do with people’s tendency to go for anything that offers an easy solution. People will always go for the new fad diet, the alternative remedy, the five dollar wrinkle trick that makes dermatologists hate you for some reason. For all that it may be well-intended, the MBTI offers a variation on that. People are very complex, variable and unpredictable. Many users of the MBTI believe that a straightforward test can simplify them to the point where they can be managed, controlled and utilised to make them as efficient and productive as possible. It’s no wonder businesses are keen to embrace something like that; it would be the ideal tool if it were guaranteed to achieve this.

So the next time you see those four letters, whether in online dating or on the job, just know that they mean essentially nothing.

More from Smithsonian.com:

Too Many Bosses in the Boardroom

Who Needs a Boss When You Have Your Co-Workers?