Saturday, October 31, 2009

Focusing on aggregates

Americans are taught to judge people individually, and in situations where you can get to know someone, this makes sense. But the truth is that you can predict aggregates better than individuals.

Using General Social Survey data, I calculated the correlation between a measure of IQ (WORDSUM) and income (REALINC) for almost 17,000 people born in the U.S.  It turned out to be .28. If you square that number, you get .08 which is called R-squared. It is interpreted as the proportion of variation in income that can be explained by your IQ. In other words, if I know one thing about a person--his IQ square--I am not going to be able to predict his income level with any accuracy at all.

But the situation changes dramatically if I calculate mean IQs and mean incomes for the 29 ethnic groups which have at least 30 respondents in each group. Now the correlation jumps all the way up to .77. If we square that, we get .59, which means that 59 percent of the variation in mean income is explained by the variation in mean IQ scores. So if I've got a random group of, say, Americans of Russian descent, chances are their average IQ is high, and I can make a pretty good bet that the group will earn an above-average income as well.

This is why Richard Lynn and Tatu Vanhanen's approach is so effective in IQ and the Wealth of Nations.  You grab a random guy in Japan, he might be smart or dumb; he might be rich or poor. But tell me the mean IQ of the country is 106, and I'm putting my money on it being a wealthy place.

HBD-ers are criticized for focusing on groups, but reality is most predictable at that level, and being scientific is being concerned with prediction.  


  1. Yes but the truth is evil.

    God must be a Nazi.

  2. dearieme3:12 PM

    "God must be a Nazi". That's certainly the impression given by the Old Testament.

  3. Damn you beat me to this.

    "HBD-ers are criticized for focusing on groups, but reality is most predictable at that level, and being scientific is being concerned with prediction. "

    This is an extremely important point. Focusing on grops doesn't preclude understanding individual variation within these larger collectives. But the stuff of nations and political scheme must inevitably focus on groups and how they will tend to act statistically.

  4. Florida resident7:15 AM

    The author meant this book by Richard Lynn and Tatu Vanhanen: IQ and Global Inequality.
    I (F.r.) actually read it. Serious book.
    Here is the book by Richard Lynn alone: IQ and the Wealth of Nations
    Also a good book.
    By the way, readers are welcome to the "history" Forum's Discussion on Amazon:
    "Human Biodiversity, history and modernity: Murray, Sailer, Derbyshire."

    Address of the first page:

    From the first post:

    //I want to open the Discussion Forum about the history and modernity of the subject of Human Biodiversity, starting from G. Spearman and his teacher and all the way down to our times. The fact that I have put three names only into the title of the Discussion, Murray, Sailer and Derbyshire, does not necessarily mean that I do not know about the existence of other outstanding scientists and deep thinkers in the sphere of Human Biodiversity (or, as it sometimes called, "Stevosphere", meaning Steve Sailer). Those three are just my favorite, while I have never met any of them personally, and Charles Murray does not suspect, that I, Florida resident, exist.

    I am not a biologist or social scientist by trade (repeat, not.) I earn my living by doing other things, which I do not want to mix with Human Biodiversity (HBD for short), and for that reason there is no information about me in the Amazon profile. HBD is just my hobby, my fun, and is the topic of my concern about my 3 kids and 2 grandkids.

    There are several places on the web, where Human Biodiversity is discussed. The owners of the corresponding sites are welcome to announce their addresses and/or duplicate the materials they consider relevant. I have no illusions that this Discussion will be better or smarter than the other ones, the more so that I am not trying to develop my own ideas in the field of HBD (do not have them). However, I have not seen an Amazon Discussion of this subject. //

    Respectfully yours, Florida resident.

  5. Focusing on aggregates

    Thanks for sharing


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