While I'm on board with the suburb criticism, I'm not sure that "per capita" is the relevant metric here. I'm concerned with the number of crime incidents per unit area, over the areas where I will most be. Is there a reason I should prefer one metric over another?

Because if you're in the area that a crime is going to occur, but it's only going to happen to k of n people in the area (with k usually equal to 1), you have a lower than certain chance of being involved?

For an example, if you're on a block there's 100% going to be a robbery in the next 5 minutes, if there are also 200 other people on that block, then you still only have a 0.5% chance of being robbed.

Essentially, because so many crimes only involve a single (or relatively few) victim(s), your odds of being involved need to account for how many other people are around you, and not just the odds that it will happen in the same area as you.

Your measure of "per unit area" doesn't account for the fact most people aren't going to be involved with the crime (eg, robbed), but will all be in the same impacted area.

So, essentially, it over-calculates how likely you actually are to be the victim of a crime. Per unit area is only useful if you want to know how close you're likely to be to a crime being committed, and not how likely you are to be the victim.

> I care about (not) being near crime

I would rather be around more crime, but victim to less of it. Your analysis trades the potential for being a victim more often to be around less total crime, which is why I think it's somewhat suspect. Perhaps that really is a trade you're willing to make, but I'm dubious.

> crime doesn't randomly sample across the set of all people, but makes me have to avoid certain times, places, and activities

Again, per capita measure is more important for figuring out if you should avoid an area than the crimes per area metric. (Also left out of this discussion is the distribution of offenses committed, which is paramount I'd argue.)

An example from where I live: there's higher crime per unit area at 9pm (it varies by time) at the mall downtown than the gas station/bowling alley/billiards room complex where the gang members loiter in the south end of town. (I looked up police numbers, because you made me curious.) But I know which one I'd rather be at based on the distribution of types of crimes and the per capita numbers. Hint: it's not the gas station.

This is a good example of higher numbers of people hiding a lower rate of victimization per person: there are literally hundreds of times more people downtown than at the gas station, so a marginally higher crime per area rate means I'm actually less likely to be involved in a crime. (Given how little of the mall you can see at once, I likely wouldn't even know it happened.)

So let me ask you: what is it you think that the crime per area figure gives you that crime per capita doesn't?

If you're concerned about the likelihood of being the victim of a crime, you should care about rates per capita. If you care about happening to be geographically near to a crime when it happens, then you should care about incidents per unit area.

The worst effects of a crime are directed against a single person--you mug or murder a human being, not a plot of land.

I'd add a caveat that many of the side effects of crimes are area dependent--a gunshot will disturb and affect the psychological wellbeing of far more people in very dense areas. That's why many people end up with an overstated impression on how common crime in cities is.

Though I think even per capita, most cities have it worse than the suburbs...

Crime rates and school rankings are the two places where the general populations inability to understand statistics really come home to roost.

Intuitively this seems right, but I wouldn't mind hearing more about what exactly the general populace is misunderstanding there.

The biggest thing with crime rates is understanding relative risk. The crime rate in another neighborhood may be 40% higher than yours, but that by itself is relatively meaningless. The reality is that in the vast majority of places in the United States you are very unlikely to be the victim of the crime. Even if you stay in a particular neighborhood for decades.

I've never been able to ascertain wether the insistence that suburbs are much safer comes from not understanding the actual risk, or something more sinister (racism - probably unintentional).

My experience was with Oakland, which probably skewed my data, to be fair. I also have only lived in CA (or outside the US entirely) so perhaps that has biased me towards thinking walkable areas like Berkeley, SF, and Santa Monica are incredibly expensive.

The Bay Area is about as skewed as you can get (outside of NYC and parts of Boston/DC). Definitely would have put a gigantic qualifier on your statement.

@enjo Especially since the best marker for performance in school is parent involvement, if you're a really involved parent the school your child is in ends up having a lot less effect than people think.

Yep I read stats that my kids results depends more on parents then on school choice. But you know what? If I have kid in shitty school, I will have to spend a lot of time and effort by supplementing that school and occasionally fighting that school. I will have to pay for tutors. I will have to look up math plans and exercises on the internet. The preparation for SAT or CAT or whatever will take more months then it would if the kid would be in a good school.

If I have a kid in good school, I can spend all that time and effort by something else. As a consequence, good school makes my kid to gain that something else and both of us to have less stressful life. I'm going to be involved too, but we will be both doing something we enjoy or something that adds bonuses on top on what school should be teaching.

That parental involvement can be both difficult and uncomfortable or pleasurable and easy. Which one it is going to be depends a lot on school choice.

Agreed. I just meant that it matters less than people think.