Video shows California police fatally shooting teenager who was reported kidnapped

A pair of handcuffs

No, people leaving an occupation does not increase the amount of people in said occupation.

That's not what I said; I was referring to the job opening being filled again, which doesn't increase the number of total cops, but will almost certainly increase the number of bad* cops. Let's say a good* cop leaves. There are two scenarios:

1. They're replaced with a bad* one. This decreases the number of good* cops and increases the number of bad* cops. This also makes the ratio worse as you noted.

2. They're not replaced, and their job position simply vanishes. This results in the loss of one good* cop and no change to the number of bad* cops. This still increases the ratio.

Assuming a little of both happen, if you're a cop who's better than average on a force that's not completely overstaffed, quitting will on average cause the absolute number of bad* cops to go up. It also definitely causes the ratio of bad* to good* to go up.

* you know what I mean

Why does that matter? I mean you're literally directly making the police force worse. Higher rates of corruption, police brutality, civil asset forfeiture, profiling, lack of will to work on hard cases... whatever bad things you don't do that the average cop does do, now get done. Whatever good things you do do that the average cop doesn't, now don't get done. That's bad.

inb4 "But the system has to get worse before it gets better!"

No, that's not really how it works. The police and justice systems in America are already at very high levels of corruption, misconduct, and straight up malice. And yet they're as strong as ever. That's because a system that's exploiting unprivileged people never breaks. If you push it to its limit, the only thing you're doing is applying more pressure to the people under their boot. You can push and push until their victims are entirely gone and only then will the system think of breaking. How much suffering are you willing to cause before that happens? How many deaths? Thousands? Millions? Even if you successfully create a civil or class war, the results won't be much better. So no, it's not a good idea or even a "so what?" idea to intentionally make the system worse. All it does is cause pain and suffering to the people who deserve it the least. That's why you should care.