In recent days, some politicians and commentators in New Zealand have attacked me for suggesting that, on average, people in higher occupational classes are brighter than people in lower class positions. I have been labelled 'extreme right wing' and a 'nut job' for pointing out the link between social class and intelligence.
Presumably, my critics wish to deny that any such link exists. For this to be true, they must demonstrate one of two things. Either, employers fill jobs randomly without regard for differences of ability between candidates; or everybody is as intelligent as everybody else. Both of these positions are absurd.
Employers try to fill jobs with the most able candidates. They don't take on the first person who walks through the door, irrespective of his or her individual qualities. Occupational recruitment is and must be selective.
But if people are to a large extent recruited to occupations on the basis of their ability, then people of higher ability will tend to be found in the higher skilled and better-paid positions in society. Evidence from IQ testing confirms this: in America, accountants and lawyers have average IQ scores of 128, compared with 122 for teachers, 109 for electricians, 96 for truck drivers and 91 for miners and farmhands.
My critics seem to find it offensive even to talk about this. I suspect they are perfectly happy accepting that sporting prowess varies across the population, and that people get selected to play for the top teams on the basis of their ability. But when it comes to intellectual, rather than physical, ability, they pretend these differences either do not exist, or are unimportant.
Why does this issue matter? Let me give two examples.
The first relates to joblessness and welfare dependency. In the last thirty years or so, all advanced economies have lost unskilled and low-skilled jobs. This is partly because new technologies have replaced menial labour, and partly because China and other developing countries can perform these tasks much cheaper. The result is that large numbers of people who used to perform useful but unchallenging tasks in the economy now have nothing to do, which is one reason why welfare numbers have increased so much.
What are governments to do about this? Assuming they don't want to leave people to waste their lives on welfare, one solution politicians find attractive is training displaced people to do more complex and rewarding jobs. The trouble is, OECD evidence shows this rarely works. Women returning to work after having children may benefit from government retraining schemes, but the long-term unemployed and jobless school-leavers rarely do.
The problem is that one-sixth of the population has an IQ under 85. At this level, people struggle with tasks like reading and understanding official documents, or working out a budget. These are the people who used to do the unskilled jobs that have now disappeared, and many of them are now long-term welfare dependent.
Pushing them through government training courses makes politicians feel good, but it is not going to turn them into skilled IT workers. Somehow, we have to find new, useful, but less challenging tasks for them to do. But if we refuse to even discuss ability differences, we will never get started on this problem.
My second example relates to equality of opportunity policies. In Britain, where I now live, the government is concerned that middle class children are still going to university in greater numbers than working class children. Politicians think there must be some unfairness in the system that explains this, so they have started withholding cash from those universities that fail to recruit more lower class entrants.
This is another example of a damaging policy being pursued because politicians refuse to acknowledge class-based differences of intelligence.
Although it is not always the case, intelligent parents tend to produce intelligent children. Given that people entering middle class jobs tend to be more intelligent, it follows that the average ability level of children born to middle class parents will tend to be higher.
We are only talking 'tendencies' and averages here. It is of course the case that many working class children are bright enough to do well in school and university and go on to well-paid, middle class jobs. Conversely, some middle class children struggle to emulate their parents' success. But the key point is that intelligence is the main influence on whether you move up or down or remain where you started. In research I have carried out in Britain, I found IQ is three times more important than parental background in predicting the occupational class that people end up in.
When politicians complain that middle class children are 'over-represented' in universities, it never occurs to them to ask whether differences of intellectual ability might have something to do with it. It is easier - more comfortable, less politically dangerous - to ignore intelligence altogether and make wild accusations about class discrimination.
The reason that I talk about class and intelligence is because it is crucial to understand these issues if we want to develop sensible social policies that generate the results we hope for. The abuse that has been directed at me in recent days has made no attempt to examine the truth or falsity of my claims. For the critics, the fact that I even discuss this issue is enough to condemn me. But wishing away uncomfortable truths does not make them disappear.