The phrase “Correlation does not imply causation” has developed in to a Falsehood, as I discuss here. This is in part because people often use the phrase to argue that a particular correlation has no meaning, which is a false argument. It is, of course, true that a correlation does not in and of itself prove a causal link between two things. And, as pointed out in a few places, but I’ll refer you to this Mother Jones piece for background, the relationship between single mothers and homicide and other crime is … well … interesting.

The idea is to blame single mothers for crime. They, being single mothers, would do a lousy job of raising their offspring, who would then grow up and be criminals. There is a racist undertone to this, with a twist. There are those who would like to blame non-white people for all the crime, and this is a version of that. The same racist “science” that underscores the link between melanin in one’s skin and criminal behavior also purports that there is a link between melanin in one’s skin and all the things that lead to single motherhood, from promiscuity to a tendency to not follow social rules to, amazingly, a shorter gestation period which would, I assume, allow single mothers to produce more offspring than might otherwise be possible.

Anyway, there are those who remember the link being made, and here is what the data for violent crime in the US looked like at the time:

The correlation between single motherhood and crime rates is clear. The single mothers must be causing the crime by producing criminal babies!

Nice relationship there. All else being equal one would want to look at these two variables and see if there is anything to the argument. We KNOW the two variables are related, because otherwise, why would anyone put them on the same graph!@!?? And, once they are on that graph they are perfectly correlated. One small thing that would need to work out is the fact that the criminals are probably not infants, but I’m sure that the time lag thing is just a detail.

Anyway, now, time has passed since that correlation seemed to be explanatory of high crime rates. Has anything changed since then? Let’s look at the data, updated:

Single mothers appear to have stopped causing crime at around 1990 or so.

Well, now that we see the whole data set, one might wonder why single motherhood rate was not correlated to crime rate prior to 1970. Maybe that’s the time lag thing. It turns out, in fact, that of the 50 years shown on this graph, the correlation seems to work for only about half the time.

Single mothers, you are off the hook. FOR NOW!

Comments

  1. #1 Philip Cohen
    November 27, 2012

    That graph is for the whole country, FYI. -pnc

  2. #2 Eric Lund
    November 28, 2012

    Well, now that we see the whole data set, one might wonder why single motherhood rate was not correlated to crime rate prior to 1970.

    Because it was the Dirty F—ing Hippies, whose numbers increased rapidly through the 1960s, that’s why. </snark>

  3. #3 Greg Laden
    November 28, 2012

    Phillip: Thanks for pointing that out, you are correct. The ORIGINAL story on which the MJ story was based discussed Washington DC specifically, as that is where the Single Mother – Homicide connection was being made. The MJ graph is better because the data are more robust.

    The DC oriented post is here: http://www.theatlantic.com/sexes/archive/2012/11/single-moms-cant-be-scapegoated-for-the-murder-rate-anymore/265576/

  4. #4 Nathaniel Cooke
    Bristol, UK
    November 30, 2012

    Statistically more broken homes &* single parents occur in poorer communities, where there is also more violent crime. In certain circumstances a lack of suitable role models may well make someone more likely to be a violent criminal, but that could just as easily happen if they had two parents who also happened to be assholes.

  5. [...] Correlation and Causation: Single Mothers and Violent Crime [Greg Laden's Blog] (scienceblogs.com) [...]

  6. #6 Diaz sebastien
    Paris
    January 3, 2013

    I m studying the structure of violent crimes on the usa and i’m very interested to see the evolution of the sungle mother during the time. My study is on recent information and based on more social statistics. I can say that the structure of the family is one of the best thing to influence the violent crimes activities. Others parameters are the poverty,the immigrant and the education.
    My site:
    http://sebastiendiazcrimesanalysis.blogspot.fr

  7. #7 IrishFarmer
    somewheres
    November 6, 2013

    Your chart, while more robust, is also misleading. You’re looking at crime as a whole, rather than on the level of demographics. The fact that chances of a person committing violent crimes rises if they were raised in a single-mother household doesn’t necessarily mean that as single motherhood increases, the overall violent crime rate will increase as well. A recent article compares this to poverty, where poverty increases the incidence of crime, but during the recession when poverty increased crime did not.

  8. […] Correlation and Causation: Single Mothers and Violent Crime [Greg Laden's Blog] (scienceblogs.com) […]

  9. #9 ScottishFarmer
    SCOTLAND OBVIOUSLY
    October 2, 2014

    Someone needs to give out trophies for worst run on sentences:

    “There is a racist undertone to this, with a twist: There are those who would like to blame non-white people for all the crime, and this is a version of that; the same racist “science” that underscores the link between melanin in one’s skin and criminal behavior also purports that there is a link between melanin in one’s skin and all the things that lead to single mother hood, from promiscuity to a tendency to not follow social rules to, amazingly, a shorter gestation period which would, I assume, allow single mothers to produce more offspring than might otherwise be possible.”

    Horrid!

  10. #10 Greg Laden
    October 2, 2014

    Well, that is not really one sentence. But it is a bit run on. Sorry for ruining your day!

    I did, though, change some of the punctuation to make it seem less like a run on sentence.

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