Tuesday, 24 September 2013

Social mobility


It is natural to note how you compare to others. In a classroom, faced with a teacher asking a question, some children will put their hands up bursting to give the answer while others will stare at the floor. In the playground some children will run fast and others slowly. There will be notable differences in fighting, crying, laughing and making friends. Some children are popular, others have no-one in particular to play with.

Run the clock forwards to the end of schooling and those differences (which will have altered somewhat because of some late maturing skills) are revealed at the next great selection. Rather than being picked for a school team activity (fearing they will be the last to be chosen) the adolescents are being picked for the best jobs (fearing they may not get a job at all). And so on, and so on, with each career step, until the peak of achievement, whenever that turns out to be. (As a rule of thumb, by the mid-40s you will have bought your most expensive house, so that is a metric of sorts).

In this way, in the great race of life, our positions are achieved and noted by others, as we note theirs. These life steps are described in terms of class and status, and the extent and pace of changes in status provide measures of social mobility.

All measures contain artefacts. Promotion in the Army is faster during a war. Soldiers die in battle, old generals are revealed as incompetent and need to be replaced, more recruits join the Army and need to be led. Similarly, economies in transition provide great opportunities. New skills lead to new businesses and new millionaires. Old industries die back. The Internet is the best current example.

In the past century the big change was from manual labour to clerical work. Interestingly, if you count social mobility only as the move from manual to clerical, then that change happened decades ago. Astoundingly, some observers still use that specific metric to say that in the UK there was lots of social mobility in the 1960s and very little now. There is certainly far less manual labour but there is much moving about from one job to another in the white collar sphere.

Writing in Prospect, Phillip Collins argues: “A boy born into the working class is no more likely to make it into the middle class now than he was in 1900. A child who is born middle class is 15 times more likely to end up middle class than a child who is born into the working class. These odds are exactly the same as they were a century ago. The boost to social mobility is a myth and so is the stalling. The truth is that Britain is a static society in which nothing has changed.”


Of course, the last line is not right. Society is not static, and much has changed, but not the rate of social mobility seen from a class of origin perspective. As Collins rightly acknowledges at the end of his article, you cannot have social mobility without one person’s rise being matched by another person’s fall. (In fact, you can fool a lot of people a lot of the time by giving them fancy job titles. We are all executive managers now). However, for real status we have to be better than someone, and worse than someone else on a socially valued metric.

The other measure of social mobility is to classify children by their parents’ occupations, determine their social class of origin, and then look at the social class they themselves eventually achieve, their class of attainment. Interesting as this measure is, it conflates two factors: the cultural impact of parenting, and the genetic contribution of parents and ancestors. These are rarely given a chance to compete fairly in the analysis, but when surrogates are used for the latter (say the child’s intelligence at 11) they are found to be very powerful.


Daniel Nettle (2003) found that a parent’s social class accounts for only 3% of the social class mobility of their children.  The ability of the individual child accounts for 13%. One could say that ability counts for four times the social mobility conferred by class of origins.

What is usually left out of the public debate is that genetics provides a testable explanation for social mobility, based purely on appointment to jobs by merit. Regression to the mean is an observable fact about the generational transmission of intelligence. On average, children are not as bright as their bright parents, and not as dull as their dull parents. The conjunction of sperm and egg does not provide precisely the same combinations each time. Exceptional genetic combinations (being very bright or very dull) are rare, and are only partially transmitted to the next generation. Throw the genetic dice often enough, and you will be likely to have an average child. Even when exceptionally bright parents have children together, they must expect that the average ability of their children will drift down somewhat to the population mean, say at least a 20% drop, possibly more depending on how you calculate the heritability estimate.

Children vary even within a family with the same mother and father, and brought up in the same home. Perhaps the current trend to smaller families makes this variability less evident, but the range of intellects within siblings is about two thirds of that encountered in the general population. It is a big range.

To put this family finding into context, first let us look at some American data from a longitudinal cohort which show the earnings of young people as they proceed from late schooling into their working careers. (Bright kids stay at school longer, delaying earning an income, but quickly make up for it).


When these aggregated data are put into a multiple regression equation comparing parental socio-economic status and the child’s IQ as predictors of their eventual income, then the standardised Beta for Parental SES is 0.1 and for IQ o.31. In this case intelligence accounts for 3 times as much variance as social class of origin.

However, one could still argue that the relationship between class and intelligence has not been teased out. A final proof of the impact of intelligence regardless of family background would be to look at the differences between siblings within families. Given the big range of intelligence to be found in an average family, this should be the final proof. If families can really bend the rules to favour their offspring, they should be able to use their family capital and connections to get all their kids into well paid jobs.

To make the matching for background as unambiguous as possible, Murray further limited the sample to pairs of subjects who were full biological siblings and who lived in the same home with both biological parents at least through the younger sibling’s seventh year. These constraints produced a sample of 3,802 individuals who comprised 2,859 unique sibling pairs. The method used was to get sibling pairs where one sibling was in the average range, and the other was above or below the average range. Above average IQ siblings were found to have excelled over their less intelligent siblings in the following ways: they had spent more years in education; they were more likely to have obtained a university first degree; they were doing work of much higher occupational prestige; they worked two more weeks in the year; and finally, they earned higher wages: In 1993, the median earnings for the average was $22,000. Their Very Bright siblings already earned a median of $11,500 more, while their Very Dull siblings earned $9,750 less. The Brights and Dulls each fell somewhere in between.

In brief, within families, brighter siblings rise in status, and even with all the string pulling in the world, duller siblings fall. It seems that family connections don’t count for as much as expected, at least not in America. Of course, rising and falling is relative to the average wage, which has usually risen since the industrial revolution, but which has had periods of stagnation.

To move towards a conclusion, in every generation families with below average intelligence parents nonetheless add some bright children to society. At the same time, every family with above average intelligence parents add some relatively duller children to society. The less bright and usually poorer families have some children who do very well, and rise in society. The brighter and usually richer families have some children who do not do well, and fall in society. Call it “intelligence mediated mobility” or “IQ churn”.

Social mobility is always there for the taking, and for primarily genetic reasons. It happens anyway, without any governmental planning. It can be stopped by repressive regimes which put barriers in the way of talented young people “from the wrong backgrounds”. It can be distorted by regimes which pick out talentless young people because they come from some chosen “correct backgrounds”.

In contrast, selecting young people by merit will maximise the chance that the best person is appointed to the job that best serves society. That will result in social mobility, as each person moves to the best job. Be warned, however, that in terms of real status, for everyone who rises there is one who falls. If status signifiers mean anything, there must be a hierarchy. A Nobel for everyone would not be a Nobel. Social mobility is good for the risers and sad for the fallers, but the real social mobility takes place when the right person is in the right job, and the whole of society rises.


  1. While I appreciate your position, and agree with it, this is going to run contrary to most sentiments. Today's orthodoxy *is* the Rawlsian edifice and that orthodoxy holds that "social mobility" is not true mobility if it is predetermined by any inputs extraneous to willed human self-determination.

    Was my last sentence gobbledygooK? Yes, it was. But, then, the entire orthodoxy is, mostly, gobbledygook so discussing it tends to produce that.

    For the bien pensant types, railing against lack of social mobility is really a means to arguing for their actual objective, a classless humanity. When you argue social mobility with philosophical liberals you are already, and inadvertently, playing the game on their home turf.

    1. If Rawls argues that "morally arbitrary factors (for example, the family one is born into) shouldn't determine one's life chances or opportunities" then I do not agree with him. I do not wish to put my child up for adoption. The family any child of mine is born into is not an arbitrary factor. It relates to my choices, and the choice to have a child is an important one, as is the choice of marital partner. I doubt those choices will ever "determine" anything in my child's life, but it is absolutely right, in my view, that my actions as a parent should influence my child's opportunities. Otherwise, I will be penalized for having saved money, spent money on education, and on books. I find it difficult to follow these enumerations of general principles, because they beg too many questions. Why waste time on them?

    2. Rawlsians play word games with terms like "arbitrary" and "contingent".

  2. "you cannot have social mobility without one person’s rise being matched by another person’s fall": hush, don't tell everyone. I used to score easy runs in common room debates when I was a fresher, just pointing out that logical necessity - sometimes by enquiring "Is it your sister whom you want to move down in society to make room for others to move up?" That used to stop 'em in their tracks. I'm all for social mobility for the reasons you point to, but I'm against not appreciating all the consequences.

  3. Two points:
    (1) "Phillip Collins argues...A child who is born middle class is 15 times more likely to end up middle class than a child who is born into the working class." Complete nonsense! Collins is mixing up odds ratios and disparity ratios. The actual advantage of the middle class child is somewhere around 3:1 or 4:1. Collins doesn't understand the statistics he is citing.
    (2) It's a pity psychologists don't read beyond their discipline. Have a look at http://www.civitas.org.uk/pdf/socialmobilitydelusions2012.pdf which covers a lot of the same ground.

  4. Dear Peter, Thanks for this excellent material, which is very useful. Odds ratios are tricky things, aren't they?

  5. I am regular reader of your blog and no doubt it all stuff is awesome. The best thing about your sharing and posting is that you always provide content that is helpful for both the newbie and experts. Looking for more stuff and tutorials.

    Love from Tech Solutions Desk