system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does a company decide a job requires X-Y number of years for a particular position?

Just scrolling through job postings. I'm qualified for a lot of jobs with the exception of 8-10 years in business XYZ or 4-5 years in industry ZYX. I know what they want and could probably hop right in and do it, but I learned many of my skills from the military or from night classes while doing a completely different job.

Why not just put, "A solid understanding of ____, ____, and ___ in the ZYX industry." Give interested candidates something more specific and can be proven in conversation or written test. 

Anyone know how they come up with the required number of years?
gpt
When it all comes down to it, they are guessing.

They know who last did the job and about how much experience they had coming into it, and in general they know that someone with more years experience will be better at it.

Besides, they can afford to discriminate.  If you post a job with no experience required then you get thousands of recent grads applying for it.  Better to ask for 3-5 years experience and then you get people for not much more who have already proven they can do the work.

I find that the 'experience required' restriction is never a deal-breaker.  It is just there to narrow the field of applicants.  The company will find out in the interview whether you know what you are doing or not, so go ahead and apply.