More policing may indeed catch more minor crimes that would otherwise go unobserved.

But the morgue has a pretty close to 100% set of data on murder victims. It's hard to argue that those are caused by catching more criminals. (And in fact, murders in high-crime neighborhoods are less likely to be solved. If anything, murders are caused by this failure to catch first-time murderers, before their second go. Their victims are also, usually, residents of the same bad neighborhoods.)

But how does the level of policing in an area affect murder rates? I don't know the answer, but from statistics I've seen, it seems pretty clear that police are not exactly great at solving murders.

Are you seriously claiming that the presence of police increases the murder rate? Or are you actually asking to know by what mechanisms policing can prevent murders?

Once you are talking about solving a murder, clearly that one was not prevented. It may draw detectives to the neighborhood looking for clues. It's pretty hard to argue that the causality runs from these detectives to the murder though.

> Are you seriously claiming that the presence of police increases the murder rate?

No, I'm not, and I didn't say anything remotely suggesting that.

Yea I couldn't figure it out. The context of the thread was which way the causality goes from density of policing to level of crime. What were you saying then?

It is hard to solve a crime when your main witness is only accessible trough Ouija board

You should ask some homicide detectives why that is.

This is somewhat tangential to your point, but I think catching more “criminals” (I.e. people who break laws, which is virtually everyone at some point - though many won’t even realize it and are unlikely to face consequences) can certainly lead to an increase in crime. In the US, at least, contact with the criminal justice system can significantly reduce social and economic opportunities and increase the likelihood that an individual will engage in future criminal activity.

"catch[ing] more criminals" was a quote from above. But I used it when discussing murder, not jaywalking.

I agree that being locked up once surely makes going straight harder (because employers are wary) and going crooked easier (as you now have more contacts). This is a real problem we should try to address. But I'm not convinced that looking the other way at violent crime is at all the right approach.

However, there is no way this is the main causal link between policing & crime. It's like suggesting that the birth rate is caused by hiring more schoolteachers in a neighborhood, ignoring the obvious fact that the city hires them (largely) based on observed need.

> I agree that being locked up once surely makes going straight harder (because employers are wary) and going crooked easier (as you now have more contacts).

It's not just a question of "going straight" - most "criminals" aren't professionals who have to make a discrete decision to stop their hypothetical "life of crime." Even if we ignore the types of "crime" that essentially involve engaging in normal behavior and being unlucky enough to get caught (ex. jaywalking, driving after having a few drinks at happy hour, or smoking marijuana) and look at violent crime, you'll find that a significant percentage of that is the result of social/psychological/economic instability and is directed at those within the social network of the individual involved. Many of these crimes are so-called "crimes of passion" or the result of some form of mental illness - in neither case is an individual likely to stop, think carefully, and rationally conclude that committing a violent crime is in their best interest.

You can lock someone like that up to prevent them from repeating actions that harm those around them, but you can only do that retroactively (which does little in material terms for victims). Given that less than half of crimes committed each year (including violent crime) are even reported to the police, and that a majority of crimes which are reported to the police aren't solved, it seems much more proactive to work towards a solution that prevents people from ending up in the type of situation that produces criminals to begin with. Proactive policing can easily be at odds with that goal if it throws petty criminals into unmanageable situations that preclude them from having a "normal" life. We can't forget that poverty itself is hugely correlated with crime.

> But I'm not convinced that looking the other way at violent crime is at all the right approach.

I don't think anyone is proposing "looking the other way" with regard to violent crime. I'm certainly not. I think it would be beneficial to make prisons more humane, in that it would increase the chance of rehabilitating them, but I don't think enacting some real-life version of "The Purge" is a reasonable course of action.

> However, there is no way this is the main causal link between policing & crime.

Oh, I definitely agree. My intention was to point out an edge case, not imply that police are the main source of crime.

This appears to be the primary concern raised in the article. But surely data scientists could put in guards against this, such as weighting the crime count versus the time spent policing the area? In fact, presumably any functional predictive policing system must already do that, else you'd just tend towards policing one area incredibly intensively.

If they are concerned about the police arrest stats or racism biasing the data set, they could keep the input to something hard to interfere with, like where murders occur or where crimes are reported by the public, rather than where arrests occur.

My opinion is that predictive policing does need regulation, but banning it entirely, to me, seems like an overreaction that will over time result in much less effective use of police resources. I suppose time will tell.

That wouldn't explain things like murder and other violent crimes. It's not like people are regularly getting murdered in the suburbs, but nobody bothered to check.

I think there are a lot of factors that go into a persons environment that influence something like murder rates.

Also, depending on what you consider a violent crime, lack of reporting / local police department's doing something about the report can very well have skew crime rates in certain areas.

Agreed, I don't think those neighborhoods just happen to have a bunch of violent people, but I keep seeing people make the naive agument that the difference in crime rate for those areas is caused by police presence. I remember after the protests in Baltimore that the police stopped doing as much proactive policing, and people who lived in the bad neighborhoods were complaining that the police weren't doing enough to prevent crime in their neighborhoods. There are underlying social issues that need to be dealt with that won't be fixed by removing police.

Violent crime can be measured by victims rather than criminals, e.g. where do homicides occur?

Do these neighborhoods commit more violent crime, rapes and murders?