It is a commonplace among racists of the `I'm not a racist, but...' variety to say things like, ``The police correctly say more black people commit crime so more are stopped.'' This is a misconception which needs to be squashed.
(Usually in this sort of discussion made-up attributes, for instance `tall' and `short', are used, rather than talking about actual ethnicities or whatever; presumably this is to avoid offending the easily-offended. Since the motto of this web log may as well be `offending the easily-offended since 2002', I won't bother.)
Suppose that there are w white people and b black people in some population. Suppose further that every so often a crime is committed, and that the victim is able accurately to report the ethnicity of the perpetrator (assume that these are muggings, or `hot' burglaries, or whatever). W crimes are recorded in which the perpetrator is white, and B in which the perpetrator is black.
Imagine that B > W; that is, more crimes are committed by black criminals than by white criminals. (In some areas of the country this is the case, we are told; these, presumably, are mostly areas with more black people than white people.) What does this tell us about the likelihood that an arbitrary black person -- such as might randomly be stopped by a police officer -- is a criminal, relative to the likelihood that an arbitrary white person is?
The answer: absolutely nothing.
The reason (which should be obvious) is that different criminals commit different numbers of crimes; the difference, that is, between `more black people commit crime' and `black people commit more crime'. These two statements are not the same.
As an extreme case, suppose that every white person commits one mugging a year, and one black person commits some large number N > w of muggings, while the rest are law-abiding. In this case, the probability of a randomly-selected white person being a criminal is 1, but the probability of a randomly-selected black person being a criminal is 1/b, a much smaller number. That is to say, in this case it is b times more likely that a random white person stopped by a police officer is a criminal than a black person is even if there are more crimes committed by black people than by white people. Without additional information about the numbers of crimes committed by individual criminals of each ethnicity, aggregate data about numbers of crimes won't tell us anything about the `propensity to crime' of white and black people.
In reality, the situation is not as extreme as in the example. Now we encounter a separate problem. Suppose that both black and white people commit crimes at the same rate, with the probabilities that an individual black or white person is a criminal being equal. In that case, the number of crimes committed by people of each ethnicity will be in proportion to the ratio of ethnicities in the general population.
Imagine that the police attempt to control crime by stopping and searching people at random (perhaps they look for stolen goods or something). Suppose further that the police are racist and stop ten times as many black people as white people. In this case, even if black and white people are equally likely to be criminals, the police will still find ten times as many black criminals as white, because everyone they stop has an equal chance of being a criminal, and they are stopping ten times as many black as white people. And, worse, their tactic is self-reinforcing, since an ill-informed police officer (or politician) might infer from the statistics that -- because so many black people are being arrested -- even more black people should be stopped and searched. But of course this is an incredibly inefficient (as well as unfair) way for the police to try to cut down on crime, since they are letting the (usually much larger) white segment of the population get away with much shallower scrutiny. And it might lead a lazy observer to conclude that black people are more likely to commit crime, while in fact what they're seeing is the effect of racist policing.
Now, all of this is just a model. The police don't investigate crime solely by stopping people at random, and there are lots of other relevant factors in criminality, some of which are correlated with race (for instance, poorer people are more likely to be criminals -- at least of the Bill the Burglar variety, if not the Martha Stewart kind -- and, sad to say, history has left black people on average poorer than white). As with so many things, the real situation is very complicated. But that's all the more reason not to make generalisations like the one which started me off on this rant.
Comments
Posted by James Fairbairn, Thursday, 25 March 2004 13:36 (link):
Well said.
Posted by edd, Friday, 26 March 2004 03:14 (link):
Yes. More ranting please.
Posted by Edmund von der Burg, Friday, 26 March 2004 09:48 (link):
Regarding the arguments in your penultimate paragraph the scenario can be changed by assuming that the detentions are not random, with some interesting results.
Say you have a police officer whose prejudice is that blacks are more likely to be criminals than whites, whereas in reality there is no difference (W = B). For this police officer to make an arrest he needs to suspect a crime, for whites they need to be running away from someone shouting 'thief', for blacks they need to look bit shifty (extreme cases here).
Inevitably this means that the officer will arrest far more blacks than whites, although a greater proportion of the whites will be successfully prosecuted. These two statistics (on their own) oppose each other, and neither reflect the true situation. As always it is possible to find anything you set out to look for - which is the point you were making.
Posted by Matthew Turner, Friday, 26 March 2004 10:06 (link):
There's also some interesting consequences of the much larger proportion of white people. Assuming criminality rates are similar, for instance, if witnesses can accurate remember the race of the alleged criminal 80% of the time, then if a witness says the criminal was black, one might assume that there is an 80% chance that they were black.
But this only holds true if hte population was 50% white, 50% black. If say it was 90% white, 10% black, then if the witness says the offender was black the probability that the offender actually was black is only 31%. Furthermore despite the fact that blacks form 10% of criminals, witnesses will say they think the criminal was black 26% of the time.
Posted by Backword Dave, Friday, 26 March 2004 16:56 (link):
There is actually a considerable body of research in the area Matthew mentions, by Tversky, Amos and Kahneman, Daniel. Most people (and their subjects were students, who ought to be a little numerate) approach statistical arguments the wrong way, even when the object of the discussion is emotionally neutral.
Posted by Paul Warren, Friday, 26 March 2004 16:31 (link):
A valid point, but where's the graph?
Posted by Pete Stevens, Saturday, 27 March 2004 13:48 (link):
For the humour impaired. This is not, and does not purport to be an official statement of police policy
Replace 'What is the probability that this person committed a crime' with 'What is the chance I can sucessfully prosecute this person for a crime[*] and get my bonus'. In this case, for good results the police should proactively target :- Poor people since they can't afford good laywers to defend themselves, so you might get them even if they're innocent.
Ethnic minorities, especially ones who have difficulty with English since any Daily Mail readers in the jury will immediately vote guilty.
The mentally ill because there's a good chance you can easily coerce them into pleading guilty.
The police should not target :-
MPs & Lords. They've probably all done something nasty but can afford lawyers to prove they didn't, and they can tie you up in court for months preventing you getting other soft targets. They'll probably prosecute you back for libel if they get off too.
Homeless people because it's a big faff to send the summons.
Pop Stars, they've *all* got cocaine but seven and a half million protesting twelve year old girls in your police station makes it hard to prosecute the easy targets.
[*] note that it's the successful prosecution that counts, not accurate prosecution.
Posted by Roy Badami, Saturday, 27 March 2004 18:22 (link):
Hmm, I think that this analysis misses what (to my mind) is the main point.
It is generally accepted that crime (well, many kinds of crime) is more likely to be committed by people who are socially disadvantaged (people with no jobs/crap jobs, etc).
So if (in some area) there's lots of crime being comitted by black people, it may well be the case that black people in this area really are more likely to be criminals than white people in the same area. But only because the proportion of the socially disadvantaged who are black is greater than the proportion of the general population in the area who are black.
So I think it's somewhat uninteresting to analyse the boundary cases where this may not be the case. Let's just accept that it is often the case, and concentrate on *why* black people in these communities generally have difficulty getting getting good jobs.
Which probably boils down to the very racism that the "I'm not a racist, but..." brigade are using the crime statistics to justify...
-roy
Posted by Chris Lightfoot, Tuesday, 30 March 2004 21:45 (link):
That's all reasonable, and the point I was making was more about the racism than about the crime. Isn't it more sensible to address the issues you raise separately as, `how do we ensure that crime is not attractive, even to people who are poor?', and `why are people in this area poorer than others outside it?' or `why are black people in the UK, on average, poorer than white people on average?' Bundling these together as `why do people in this area commit more crime?' or whatever just confuses the issue and encourages the racists.
Posted by martin joyce, Thursday, 11 August 2005 10:34 (link):
There are lies, damned lies and statistics. It seems to me the liberal elite are bound and determined to misrepresent the truth by statistics albeit in a well meaning but hopelessly misguided attempt to undermine racist arguments. In London, people who are robbed in the street will say, I believe, in about 80% of cases, that the perpetrator was black by which they usually mean afro-carribean. If afro-carribeans make up around 15% of the population I estimate that it means an afro-carribean is about 20 times more likely to attack you in the street than a non-afro carribean. (15AC=80 thus 1AC = 5.33, 85 non-AC=20 thus 1 non AC=0.24, 5.33/0.24 = 22 but say 20) Young suspect black males should therefore be stopped by the police far more often than whites until robberies by blacks become a thing of the past.
The reason for this alarming reality is that street crime is a culture amongst a large section of alienated young black males living in poverty and from broken homes. What is rarely admitted is that their actions bear down most heavily on the black community who are, as a result, naturally distrusted and feared by the white community. We should as a white society be helping blacks to build a monied property owning middle class with families that stay together. Conservative blacks would welcome a clamping down on 'hoodies' and all forms of anti-social behaviour, praise of gang culture in music etc. Its not hip, its sick.
Liberals who bend the truth and statistics do only harm. The truth is most blacks are far more conservative than whites and if they have money send their children abroad to schools that provide a better framework of discipline and which have higher expectations. Whites need to listen to that conservative section of the black community and help them and not spend their time trying to avoid the truth. Blacks want and need black crime to stop more than whites.
Posted by Pete Stevens, Thursday, 11 August 2005 12:54 (link):
Percentage of the population that is Black African, Black Carribbean or Black Other = 2%
http://www.statistics.gov.uk/cci/nugger.asp?id=273
When criticising others for their statistics it is important that your own statistics bear a vague resemblance to reality, especially if you're using it to back up a racist policy.
Would a better policy for the police merely be to stop the people they suspect of committing the crimes irrespective of skin colour? Would a good idea be to try and eliminate poverty - irrespective of the skin colour of the poor person? Would it be a good idea to improve education and schools in poor areas - irrespective of the skin colour of the people who live there?
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