Have you ever thought about how many people in your job actually know what they’re doing?

It’s a question that got me curious, so I asked a bunch of folks in different fields. Usually, when we think about how people perform at work, it looks like this: 20% are really great, 70% are just okay, and 10% are not doing well at all.

So, if you asked someone, “How many people in your field are really good at what they do?” you’d think their answer would be similar. But that’s not what I found out.

Take a minute to think about your own job. How many of your coworkers do you think are really good at it? If you’re an electrician and I asked you about ten other electricians, would you say that 80-90% of them can do a great job? What if you’re in HR—how many of your peers do you think are truly skilled?

In a survey I did a while back, only 1% of 394 professionals thought that more than 90% of their colleagues knew what they were doing.

On the other hand, a surprising 18% felt that less than 10% of their peers were really competent. What!?

This shows that people often think they’re better at their jobs than their coworkers are. It’s hard to say, “Yes, Karen is much better than me,” but it’s easy to say, “Oh, Tim? He doesn’t know what he’s doing!”

In my experience looking at different companies, I’ve seen that most people can handle the simple parts of their job. But when things get complicated, you start to see who’s really good and who’s not.

This is kind of scary when you think about it.

Jobs that need a lot of skill—like in medicine, law, finance, and tech—require good education, experience, ongoing learning, and attention to detail. Many people want these jobs because they pay well and there are lots of openings, but not everyone has what it takes to be good at them.

If you’ve ever had a medical problem where doctors couldn’t figure out what was wrong, and then you finally got answers at a top hospital, you know how much difference skill can make. The same goes for a tough legal situation—you can really tell the difference between a cheaper lawyer and an expensive one.

The gap in skills and performance among coworkers is probably bigger than we think. The idea that 20% of people in any field are top performers is likely too high; it’s probably closer to 1%. Real stars in any profession are rare. That’s why it’s so important for companies to keep their top talent. These people usually do a lot better than a bunch of average or below-average workers doing the same job.