12, but it’s complicated. I was a freelancer for a long time, count that as one job, but I had dozens of customers. I quit one place and went back, and 2 employers have been acquired while I worked there, count all those as one each. Not counting summer or part times while in school. This is all over the span of 44 years, so I’m a little quicker than your 4 years on average. The shortest one was a little less than a year; it was a mistake to take the job in the first place. IMO, switching jobs is the biggest, maybe the only, leverage a worker has vs an employer. If you don’t have a credible alternative to your job, they know that, and know they can victimize you.
I am sure they are aware of it. I think it’s like us and horses: yes, this creature is much larger and could hurt or kill me if it wanted to, but horses are basically cool and friendly and we trust them.
I’ve been with my SO for more than 4 years, and I often don’t understand her motivations either.