On August 31, 2003, I posted IQ and Populations, which to this day remains my second most popular post.  Unlike Tyranny of Email, my most popular article, the reaction is not generally positive.  The post is popular in the sense of being widely linked, but unpopular in the sense of being widely disputed.  While Tyranny asserts opinions that nearly everyone agrees with, IQ and Populations reviews facts with which nearly everyone disagrees. 

Just today I received a friendly email which stated with confidence: "I just wanted to assure you that regardless of studies and debatable ideas such as IQ measurements, the world is unlikely to become any dumber because of a larger number of Indians as a proportion of the world population."  My correspondent goes on to write "It is difficult to see how you could buy the argument that an entire population of over a billion people in some intellectual way scores lower on a standardized IQ test."

Here's what I replied:

Thank you for your email.  It is gratifying to get a response to posts I made four years ago, and this one still gets a lot of traffic.

Here’s something to consider… if I were to say that the average height as measured of the population of India was smaller than the average height as measured from the population of the Netherlands, I believe you would not disagree.  Furthermore the average height as measured of Indians is larger than that of Chinese.  These are not controversial statements.  And of course any given Indian or Dutchman or Chinese can be much taller or shorter than the average.

Yet if similar statements are made for measured IQ, people get very uncomfortable.  It seems harder to believe that the average measured IQ for distinct populations would be exactly the same than to believe there would be some difference, yet when a study shows such a difference to exist, it is immediately discredited.  Not only could I buy this argument, but it is not based on opinion, it is based on fact.  Different populations have different measured characteristics for height – and for IQ.  And of course as with height, any given individual can vary widely from the average; in fact the variations within each population are larger than the differences between the averages.

I believe the discomfort from this measured result is because measured IQ is not only a proxy for intelligence, it is a proxy for worth.  Unlike height or other mundane physical characteristics which seem at best loosely correlated with “success”, measured IQ and intelligence are strongly correlated.  This is why people are so eager to discredit first the measurements of IQ and secondly the correlation of IQ to intelligence.

Finally, given that average measured IQ differs between populations, and since measured IQ is hereditary – whether genetically based or purely a result of environment, or some combination, study after study has shown that measured IQ of parents is strongly correlated to measured IQ of their children – it follows that the relative birth rates of different populations will affect the overall measured IQ of people in general.  It may be an uncomfortable conclusion but it follows logically from the facts.

Cheers, and thanks again for your email…

So, is this really true?  Yes.  Is this uncomfortable?  Yes.  Is this important?  Yes.

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